However, you are much more likely to obtain helpful responses if you tell us what you have attempted and explain where you are stuck. Questions that do not include that information tend to be closed. As for the remarks about the Inclusion-Exclusion Principle and the algorithm, I interpreted them as calls for alternative solutions. $\endgroup$pigeon hole principle and principle of inclusion-exclusion 2 Pigeon Hole Principle The pigeon hole principle is a simple, yet extremely powerful proof principle. Informally it says that if n +1 or more pigeons are placed in n holes, then some hole must have at least 2 pigeons. This is also known as the Dirichlet’s drawer principle or ... The way I usually think of the Inclusion-Exclusion Principle goes something like this: If something is in n of the S j, it will be counted ( n k) times in the sum of the sizes of intersections of k of the S j. Therefore, it will be counted. (1) ∑ k ≥ 1 ( − 1) k − 1 ( n k) = 1. time in the expression.包除原理 （ほうじょげんり、 英: Inclusion-exclusion principle, principle of inclusion and exclusion, Principle of inclusion-exclusion, PIE ）あるいは包含と排除の原理とは、 数え上げ組合せ論 における基本的な結果のひとつ。. 特別な場合には「 有限集合 A と B の 和集合 に属する ... pigeon hole principle and principle of inclusion-exclusion 2 Pigeon Hole Principle The pigeon hole principle is a simple, yet extremely powerful proof principle. Informally it says that if n +1 or more pigeons are placed in n holes, then some hole must have at least 2 pigeons. This is also known as the Dirichlet’s drawer principle or ...The inclusion-exclusion principle states that to count the unique ways of performing a task, we should add the number of ways to do it in a single way and the number of ways to do it in another way and then subtract the number of ways to do the task that is common to both the sets of ways. In general, if there are, let’s say, 'N' sets, then ...The Inclusion-Exclusion Principle (for two events) For two events A, B in a probability space: P(A ...\end{align*}\] Thus, the inclusion-exclusion formula counts each element of the union exactly once. ∎. Positive Integer Equations. As an example, the principle of inclusion-exclusion can be used to answer some questions about solutions in the integers. How many solutions are there to \(x+y+z=15\) where each variable is a non-negative integer? Apr 17, 2016 · You might take out those divisible by $2,3,5,7$ (all the primes up to $\sqrt{100}$). Doing this is a pretty straightforward includsion-exclusion counting, and this has the effect of counting the number of primes between $10$ and $100$. Mar 26, 2020 · Inclusion-exclusion principle question - 3 variables. There are 3 types of pants on sale in a store, A, B and C respectively. 45% of the customers bought pants A, 35% percent bought pants B, 30% bought pants C. 10% bought both pants A & B, 8% bought both pants A & C, 5% bought both pants B & C and 3% of the customers bought all three pairs. Notes on the Inclusion Exclusion Principle The Inclusion Exclusion Principle Suppose that we have a set S consisting of N distinct objects. Let A1; A2; :::; Am be a set of properties that the objects of the set S may possess, and let N(Ai) be the number of objects having property Ai: Note Week 6-8: The Inclusion-Exclusion Principle March 13, 2018 1 The Inclusion-Exclusion Principle Let S be a finite set. Given subsets A,B,C of S, we haveIt follows that the e k objects with k of the properties contribute a total of ( k m) e k to e m and hence that. (1) s m = ∑ k = m r ( k m) e k. Now I’ll define two polynomials: let. S ( x) = ∑ k = 0 r s k x k and E ( x) = ∑ k = 0 r e k x k. In view of ( 1) we have.In combinatorics, a branch of mathematics, the inclusion–exclusion principle is a counting technique which generalizes the familiar method of obtaining the number of elements in the union of two finite sets; symbolically expressed as where A and B are two finite sets and |S | indicates the cardinality of a set S . The formula expresses the fact that the sum of the sizes of the two sets may ...Notes on the Inclusion Exclusion Principle The Inclusion Exclusion Principle Suppose that we have a set S consisting of N distinct objects. Let A1; A2; :::; Am be a set of properties that the objects of the set S may possess, and let N(Ai) be the number of objects having property Ai: NoteThe principle of inclusion and exclusion (PIE) is a counting technique that computes the number of elements that satisfy at least one of several properties while guaranteeing that elements satisfying more than one property are not counted twice.the static version of the distinction inclusion/exclusion for addressing the emergence of new inequalities (section IV). On this basis, section V proposes an original classification of different constellations of inclusion/exclusion and illustrates them with specific examples. Section VI offers a summary of the main findings together withThe principle of Inclusion-Exclusion is an effective way to calculate the size of the individual set related to its union or capturing the probability of complicated events. Takeaways Inclusion and exclusion criteria increases the likelihood of producing reliable and reproducible results.This formula makes sense to me again, but can someone please explain it to me in simple terms how the binomial theorem is even related to inclusion/exclusion? I've also seen proofs where examples substitute the x = 1 and y = -1 and we end up getting the binomial expansion to equal 0. I just don't see how we can relate that to PIE. Please help ...Homework Statement Suppose that p and q are prime numbers and that n = pq. Use the principle of inclusion-exclusion to find the number of positive integers not exceeding n that are relatively prime to n. Homework Equations Inclusion-Exclusion The Attempt at a Solution The...Inclusion-Exclusion and its various Applications. In the field of Combinatorics, it is a counting method used to compute the cardinality of the union set. According to basic Inclusion-Exclusion principle : For 2 finite sets and , which are subsets of Universal set, then and are disjoint sets. .Nov 21, 2018 · A thorough understanding of the inclusion-exclusion principle in Discrete Mathematics is vital for building a solid foundation in set theory. With the inclusion-exclusion principle, there are generally two types of questions that appear in introductory and lower level Discrete Mathematics syllabi. These question types are: And let A A be a set of elements which has some of these properties. Then the Inclusion-Exclusion Principle states that the number of elements with no properties at all is. This is perfectly fine, but he finishes his two-page paper with a Generalized version of Inclusion-Exclusion Principle. Let t1, ⋯,tn t 1, ⋯, t n be commuting ...This proves the principle of inclusion-exclusion. Although the proof seems very exciting, I am confused because what the author has proved is $1=1$ from the LHS and RHS. Thus, is this still a valid proof? We need to prove that the total cardinality of LHS is the RHS. The RHS produces a $1$ for each member of the union of the sets.Using inclusion-exclusion principle to find the probability of events. 2. Find the correspondence between natural numbers and subsets with the inclusion-exclusion ...Principle of Inclusion and Exclusion is an approach which derives the method of finding the number of elements in the union of two finite sets. This is used to solve combinations and probability problems when it is necessary to find a counting method, which makes sure that an object is not counted twice. Consider two finite sets, A and B. The question wants to count certain arrangements of the word "ARRANGEMENT": a) find exactly 2 pairs of consecutive letters?. b) find at least 3 pairs of consecutive letters?. I have the answer given from the tutor but it doesn't make sense to me. Full Course of Discrete Mathematics: https://youtube.com/playlist?list=PLV8vIYTIdSnZjLhFRkVBsjQr5NxIiq1b3In this video you can learn about Principle of Inclu...Nov 21, 2018 · A thorough understanding of the inclusion-exclusion principle in Discrete Mathematics is vital for building a solid foundation in set theory. With the inclusion-exclusion principle, there are generally two types of questions that appear in introductory and lower level Discrete Mathematics syllabi. These question types are: You should not have changed the symbols on the left side of the equation! On the left you should have $\cup$, on the right you should have $\cap$. Look at your book again. You will not be able to complete the exercise until you, very slowly and carefully, understand the statement of the inclusion-exclusion principle. $\endgroup$ –The lesson accompanying this quiz and worksheet called Inclusion-Exclusion Principle in Combinatorics can ensure you have a quality understanding of the following: Description of basic set theory ...Dec 3, 2014 · You can set up an equivalent question. Subtract out 4 4 from both sides so that 0 ≤x2 ≤ 5 0 ≤ x 2 ≤ 5. Similarly, subtract out 7 7 so 0 ≤ x3 ≤ 7 0 ≤ x 3 ≤ 7. This leaves us with x1 +x2 +x3 = 7 x 1 + x 2 + x 3 = 7. We can use a generating function to give us our inclusion-exclusion formula. The inclusion and exclusion (connection and disconnection) principle is mainly known from combinatorics in solving the combinatorial problem of calculating all permutations of a finite set or ...This set of Discrete Mathematics Multiple Choice Questions & Answers (MCQs) focuses on “Discrete Probability – Principle of Inclusion Exclusion”. 1. There are 70 patients admitted in a hospital in which 29 are diagnosed with typhoid, 32 with malaria, and 14 with both typhoid and malaria. Find the number of patients diagnosed with typhoid ...Mar 26, 2020 · Inclusion-exclusion principle question - 3 variables. There are 3 types of pants on sale in a store, A, B and C respectively. 45% of the customers bought pants A, 35% percent bought pants B, 30% bought pants C. 10% bought both pants A & B, 8% bought both pants A & C, 5% bought both pants B & C and 3% of the customers bought all three pairs. Using inclusion-exclusion principle to count the integers in $\{1, 2, 3, \dots , 100\}$ that are not divisible by $2$, $3$ or $5$ Ask Question Principle of Inclusion-Exclusion. The Principle of Inclusion-Exclusion (abbreviated PIE) provides an organized method/formula to find the number of elements in the union of a given group of sets, the size of each set, and the size of all possible intersections among the sets.The principle of inclusion and exclusion (PIE) is a counting technique that computes the number of elements that satisfy at least one of several properties while guaranteeing that elements satisfying more than one property are not counted twice.Nov 4, 2021 · The inclusion-exclusion principle is similar to the pigeonhole principle in that it is easy to state and relatively easy to prove, and also has an extensive range of applications. These sort of ... The principle of inclusion-exclusion says that in order to count only unique ways of doing a task, we must add the number of ways to do it in one way and the number of ways to do it in another and then subtract the number of ways to do the task that are common to both sets of ways. The principle of inclusion-exclusion is also known as the ...In combinatorics, a branch of mathematics, the inclusion–exclusion principle is a counting technique which generalizes the familiar method of obtaining the number of elements in the union of two finite sets; symbolically expressed as where A and B are two finite sets and |S | indicates the cardinality of a set S . The formula expresses the fact that the sum of the sizes of the two sets may ... Feb 1, 2017 · PDF | Several proofs of the Inclusion-Exclusion formula and ancillary identities, plus a few applications. See the later version (Aug 11, 2017 -- I... | Find, read and cite all the research you ... Oct 10, 2014 · The Principle of Inclusion-Exclusion. Example 1: In a discrete mathematics class every student is a major in computer science or mathematics , or both. The number of students having computer science as a major (possibly along with mathematics) is 25; 5: The Principle of Inclusion and Exclusion 4.4: Generating Functions (Exercises) 5.1: The Size of a Union of Sets Kenneth P. Bogart Dartmouth University One of our very first counting principles was the sum principle which says that the size of a union of disjoint sets is the sum of their sizes.The Inclusion-Exclusion Principle can be used on A n alone (we have already shown that the theorem holds for one set): X J fng J6=; ( 1)jJj 1 \ i2 A i = ( 1)jfngj 1 \Jan 1, 1980 · The principle of inclusion and exclusion is very important and useful for enumeration problems in combinatorial theory. By using this principle, in the chapter, the number of elements of A that satisfy exactly r properties of P are deduced, given the numbers of elements of A that satisfy at least k ( k ≥ r) properties of P. Principle of Inclusion-Exclusion. The Principle of Inclusion-Exclusion (abbreviated PIE) provides an organized method/formula to find the number of elements in the union of a given group of sets, the size of each set, and the size of all possible intersections among the sets.is to present several deriv ations of the inclusion-exclusion formula and various ancillary form ulas and to give a few examples of its use. Let S be a set of n elements with n ≥ 1, and let S 1 ...The Inclusion-Exclusion Principle. The inclusion-exclusion principle is an important combinatorial way to compute the size of a set or the probability of complex events. It relates the sizes of individual sets with their union. Statement The verbal formula. The inclusion-exclusion principle can be expressed as follows:The Inclusion-Exclusion Principle can be used on A n alone (we have already shown that the theorem holds for one set): X J fng J6=; ( 1)jJj 1 \ i2 A i = ( 1)jfngj 1 \Inclusion/Exclusion with 4 Sets • Suppose you are using the inclusion-exclusion principle to compute the number of elements in the union of four sets. –Each set has 15 elements. –The pair-wise intersections have 5 elements each. –The three-way intersections have 2 elements each. –There is only one element in the intersection of all ... Apr 17, 2016 · You might take out those divisible by $2,3,5,7$ (all the primes up to $\sqrt{100}$). Doing this is a pretty straightforward includsion-exclusion counting, and this has the effect of counting the number of primes between $10$ and $100$. Inclusion-Exclusion Principle with introduction, sets theory, types of sets, set operations, algebra of sets, multisets, induction, relations, functions and algorithms etc.Induction Step. Consider f(⋃i= 1r Ai ∩Ar+1) f ( ⋃ i = 1 r A i ∩ A r + 1) . By the fact that Intersection Distributes over Union, this can be written: At the same time, we have the expansion of the term f(⋃i= 1r Ai) f ( ⋃ i = 1 r A i) to take into account. So we can consider the general term of s s intersections in the expansion of f ...The Inclusion-Exclusion Principle (for two events) For two events A, B in a probability space: P(A ...Jun 7, 2023 · Induction Step. Consider f(⋃i= 1r Ai ∩Ar+1) f ( ⋃ i = 1 r A i ∩ A r + 1) . By the fact that Intersection Distributes over Union, this can be written: At the same time, we have the expansion of the term f(⋃i= 1r Ai) f ( ⋃ i = 1 r A i) to take into account. So we can consider the general term of s s intersections in the expansion of f ... By Bonferroni's inequalities, the terms in the inclusion-exclusion sum alternately under- and over-estimate the final value. You should be fine with just: $$ \lvert A_1 \cup A_2 \cup \ldots \cup A_n \rvert \ge \sum_i \lvert A_i \rvert - \sum_{i < j} \lvert A_i \cap A_j \rvert \ge \sum_i \lvert A_i \rvert - \sum_{i < j} a_{ij} $$ This bound can ...A well-known application of the inclusion–exclusion principle is to the combinatorial problem of counting all derangements of a finite set. A derangement of a set A is a bijection from A into itself that has no fixed points. Via the inclusion–exclusion principle one can show that if the cardinality of A is n, then the number of derangements isThis video contains the description about principle of Inclusion and Exclusion Aug 4, 2013 · Last post was a proof for the Inclusion-Exclusion Principle and now this post is a couple of examples using it. The first example will revisit derangements (first mentioned in Power of Generating Functions); the second is the formula for Euler's phi function. Yes, many posts will end up mentioning Euler … 1 Answer. It might be useful to recall that the principle of inclusion-exclusion (PIE), at least in its finite version, is nothing but the integrated version of an algebraic identity involving indicator functions. 1 −1A =∏i=1n (1 −1Ai). 1 − 1 A = ∏ i = 1 n ( 1 − 1 A i). Integrating this pointwise identity between functions, using ... Jun 15, 2015 · And let A A be a set of elements which has some of these properties. Then the Inclusion-Exclusion Principle states that the number of elements with no properties at all is. This is perfectly fine, but he finishes his two-page paper with a Generalized version of Inclusion-Exclusion Principle. Let t1, ⋯,tn t 1, ⋯, t n be commuting ... TheInclusion-Exclusion Principle Physics 116C Fall 2012 TheInclusion-Exclusion Principle 1. The probability that at least one oftwoevents happens Consider a discrete sample space Ω. We define an event A to be any subset of Ω, which in set notation is written as A⊂ Ω. Then, Boas asserts in eq. (3.6) on p. 732 that1 Number of solutions to an equation using the inclusion-exclusion principle 3 Given $3$ types of coins, how many ways can one select $20$ coins so that no coin is selected more than $8$ times.the static version of the distinction inclusion/exclusion for addressing the emergence of new inequalities (section IV). On this basis, section V proposes an original classification of different constellations of inclusion/exclusion and illustrates them with specific examples. Section VI offers a summary of the main findings together with The question wants to count certain arrangements of the word "ARRANGEMENT": a) find exactly 2 pairs of consecutive letters? b) find at least 3 pairs of consecutive letters? I have the ans...1 Answer. It might be useful to recall that the principle of inclusion-exclusion (PIE), at least in its finite version, is nothing but the integrated version of an algebraic identity involving indicator functions. 1 −1A =∏i=1n (1 −1Ai). 1 − 1 A = ∏ i = 1 n ( 1 − 1 A i). Integrating this pointwise identity between functions, using ... The Inclusion-Exclusion Principle. The inclusion-exclusion principle is an important combinatorial way to compute the size of a set or the probability of complex events. It relates the sizes of individual sets with their union. Statement The verbal formula. The inclusion-exclusion principle can be expressed as follows:Number of solutions to an equation using the inclusion-exclusion principle 3 Given $3$ types of coins, how many ways can one select $20$ coins so that no coin is selected more than $8$ times. Dec 3, 2014 · You can set up an equivalent question. Subtract out 4 4 from both sides so that 0 ≤x2 ≤ 5 0 ≤ x 2 ≤ 5. Similarly, subtract out 7 7 so 0 ≤ x3 ≤ 7 0 ≤ x 3 ≤ 7. This leaves us with x1 +x2 +x3 = 7 x 1 + x 2 + x 3 = 7. We can use a generating function to give us our inclusion-exclusion formula. Notes on the Inclusion Exclusion Principle The Inclusion Exclusion Principle Suppose that we have a set S consisting of N distinct objects. Let A1; A2; :::; Am be a set of properties that the objects of the set S may possess, and let N(Ai) be the number of objects having property Ai: Note The principle of inclusion and exclusion is very important and useful for enumeration problems in combinatorial theory. By using this principle, in the chapter, the number of elements of A that satisfy exactly r properties of P are deduced, given the numbers of elements of A that satisfy at least k ( k ≥ r) properties of P.The Inclusion-Exclusion Principle can be used on A n alone (we have already shown that the theorem holds for one set): X J fng J6=; ( 1)jJj 1 \ i2 A i = ( 1)jfngj 1 \ Sep 14, 2018 · This formula makes sense to me again, but can someone please explain it to me in simple terms how the binomial theorem is even related to inclusion/exclusion? I've also seen proofs where examples substitute the x = 1 and y = -1 and we end up getting the binomial expansion to equal 0. I just don't see how we can relate that to PIE. Please help ... The Inclusion-Exclusion Principle can be used on A n alone (we have already shown that the theorem holds for one set): X J fng J6=; ( 1)jJj 1 \ i2 A i = ( 1)jfngj 1 \ Mar 26, 2020 · Inclusion-exclusion principle question - 3 variables. There are 3 types of pants on sale in a store, A, B and C respectively. 45% of the customers bought pants A, 35% percent bought pants B, 30% bought pants C. 10% bought both pants A & B, 8% bought both pants A & C, 5% bought both pants B & C and 3% of the customers bought all three pairs. The principle of inclusion and exclusion (PIE) is a counting technique that computes the number of elements that satisfy at least one of several properties while guaranteeing that elements satisfying more than one property are not counted twice. University of Pittsburgh The principle of inclusion and exclusion is very important and useful for enumeration problems in combinatorial theory. By using this principle, in the chapter, the number of elements of A that satisfy exactly r properties of P are deduced, given the numbers of elements of A that satisfy at least k ( k ≥ r) properties of P.\end{align*}\] Thus, the inclusion-exclusion formula counts each element of the union exactly once. ∎. Positive Integer Equations. As an example, the principle of inclusion-exclusion can be used to answer some questions about solutions in the integers. How many solutions are there to \(x+y+z=15\) where each variable is a non-negative integer? By the principle of inclusion-exclusion, jA[B[Sj= 3 (219 1) 3 218 + 217. Now for the other solution. Instead of counting study groups that include at least one of Alicia, Bob, and Sue, we will count study groups that don’t include any of Alicia, Bob, or Sue. To form such a study group, we just need to choose at least 2 of the remaining 17 ... The principle of inclusion and exclusion (PIE) is a counting technique that computes the number of elements that satisfy at least one of several properties while guaranteeing that elements satisfying more than one property are not counted twice.By the principle of inclusion-exclusion, jA[B[Sj= 3 (219 1) 3 218 + 217. Now for the other solution. Instead of counting study groups that include at least one of Alicia, Bob, and Sue, we will count study groups that don’t include any of Alicia, Bob, or Sue. To form such a study group, we just need to choose at least 2 of the remaining 17 ... Due to the duality between union and intersection, the inclusion–exclusion principle can be stated alternatively in terms of unions or intersections. The inclusion-exclusion principle is similar to the pigeonhole principle in that it is easy to state and relatively easy to prove, and also has an extensive range of applications. These sort of ...Oct 12, 2015 · The way I usually think of the Inclusion-Exclusion Principle goes something like this: If something is in n of the S j, it will be counted ( n k) times in the sum of the sizes of intersections of k of the S j. Therefore, it will be counted. (1) ∑ k ≥ 1 ( − 1) k − 1 ( n k) = 1. time in the expression. You need to exclude the empty set in your sum. Due to the duality between union and intersection, the inclusion–exclusion principle can be stated alternatively in terms of unions or intersections.The principle of inclusion-exclusion says that in order to count only unique ways of doing a task, we must add the number of ways to do it in one way and the number of ways to do it in another and then subtract the number of ways to do the task that are common to both sets of ways. The principle of inclusion-exclusion is also known as the ...The principle of inclusion and exclusion is very important and useful for enumeration problems in combinatorial theory. By using this principle, in the chapter, the number of elements of A that satisfy exactly r properties of P are deduced, given the numbers of elements of A that satisfy at least k ( k ≥ r) properties of P.The principle of inclusion-exclusion is an important result of combinatorial calculus which finds applications in various fields, from Number Theory to Probability, Measurement Theory and others. In this article we consider different formulations of the principle, followed by some applications and exercises.
Week 6-8: The Inclusion-Exclusion Principle March 13, 2018 1 The Inclusion-Exclusion Principle Let S be a finite set. Given subsets A,B,C of S, we have . Facharzt psychiatrie und psychotherapie
Write out the explicit formula given by the principle of inclusion–exclusion for the number of elements in the union of six sets when it is known that no three of these sets have a common intersection. The Inclusion-Exclusion Principle can be used on A n alone (we have already shown that the theorem holds for one set): X J fng J6=; ( 1)jJj 1 \ i2 A i = ( 1)jfngj 1 \ Inclusion-Exclusion and its various Applications. In the field of Combinatorics, it is a counting method used to compute the cardinality of the union set. According to basic Inclusion-Exclusion principle : For 2 finite sets and , which are subsets of Universal set, then and are disjoint sets. .5.4: The Principle of Inclusion and Exclusion (Exercises) 1. Each person attending a party has been asked to bring a prize. The person planning the party has arranged to give out exactly as many prizes as there are guests, but any person may win any number of prizes. If there are n n guests, in how many ways may the prizes be given out so that ...Proof Consider as one set and as the second set and apply the Inclusion-Exclusion Principle for two sets. We have: Next, use the Inclusion-Exclusion Principle for two sets on the first term, and distribute the intersection across the union in the third term to obtain: Now, use the Inclusion Exclusion Principle for two sets on the fourth term to get: Finally, the set in the last term is just ... Inclusion exclusion principle: Counting ways to do bridge hands 0 How many eight-card hands can be chosen from exactly 2 suits/13-card bridge hands contain six cards one suit and four and three cards of another suitsJul 29, 2021 · 5.4: The Principle of Inclusion and Exclusion (Exercises) 1. Each person attending a party has been asked to bring a prize. The person planning the party has arranged to give out exactly as many prizes as there are guests, but any person may win any number of prizes. If there are n n guests, in how many ways may the prizes be given out so that ... the static version of the distinction inclusion/exclusion for addressing the emergence of new inequalities (section IV). On this basis, section V proposes an original classification of different constellations of inclusion/exclusion and illustrates them with specific examples. Section VI offers a summary of the main findings together withAug 31, 2019 · It seems that this formula is similar to an inclusion-exclusion formula? One approach I was thinking was an induction approach. Obviously if we take $|K|=1$ the formula holds. The induction step could be to assume it holds for $|K-1|-1$ and then simply prove the final result. Does this seem a viable approach, any other suggested approaches are ... Inclusion exclusion principle: Counting ways to do bridge hands 0 How many eight-card hands can be chosen from exactly 2 suits/13-card bridge hands contain six cards one suit and four and three cards of another suitsCounting intersections can be done using the inclusion-exclusion principle only if it is combined with De Morgan’s laws of complementing. a) true. b) false. View Answer. 10. Using the inclusion-exclusion principle, find the number of integers from a set of 1-100 that are not divisible by 2, 3 and 5. a) 22. b) 25. c) 26.You need to exclude the empty set in your sum. Due to the duality between union and intersection, the inclusion–exclusion principle can be stated alternatively in terms of unions or intersections..
