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How many twoelement subsets of {1,2,3,4} are there that do not [#permalink]
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01 Nov 2016, 02:55
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How many twoelement subsets of {1,2,3,4} are there that do not contain the pair of elements 2 and 4? (a) One (b) Two (c) Four (d) Five (e) Six
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Re: How many twoelement subsets of {1,2,3,4} are there that do not [#permalink]
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01 Nov 2016, 04:04
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srijatverma wrote: How many twoelement subsets of {1,2,3,4} are there that do not contain the pair of elements 2 and 4?
(a) One (b) Two (c) Four (d) Five (e) Six {1,2}, {1,3}, {1,4}, {2,3}, {3,4}. Or: \(C^2_41=5\). Answer: D.
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Re: How many twoelement subsets of {1,2,3,4} are there that do not [#permalink]
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14 Sep 2017, 23:07
Bunuel, Could you please explain why do you deduct one?



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Re: How many twoelement subsets of {1,2,3,4} are there that do not [#permalink]
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14 Sep 2017, 23:23
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Re: How many twoelement subsets of {1,2,3,4} are there that do not [#permalink]
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15 Sep 2017, 02:38
Why we should not delete 2, one for (4,2) also Sent from my XT1045 using GMAT Club Forum mobile app



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Re: How many twoelement subsets of {1,2,3,4} are there that do not [#permalink]
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15 Sep 2017, 02:46
vs224 wrote: Why we should not delete 2, one for (4,2) also Sent from my XT1045 using GMAT Club Forum mobile appA set, by definition, is a collection of elements without any order. While, a sequence, by definition, is an ordered list of terms. 4C2 = 6 is the number of different twoelement subsets from {1, 2, 3, 4} without the order: {1,2}, {1,3}, {1,4}, {2,3}, {2,4}, {3,4}. Only 1 one subset, namely {2,4}, should be subtracted.
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How many twoelement subsets of {1,2,3,4} are there that do not [#permalink]
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15 Sep 2017, 12:00
srijatverma wrote: How many twoelement subsets of {1,2,3,4} are there that do not contain the pair of elements 2 and 4?
(a) One (b) Two (c) Four (d) Five (e) Six You can list the subsets in about 30 seconds. {1,2,3,4} Twoelement subsets that do not contain the pair of elements 2 and 4 Element 1 paired with each possibility Element 2 paired with each possibility Element 3  same {1,2} {1,3} {1,4} {2,3} {3,4} There are 5 subsets that satisfy the conditions of the prompt. Answer D
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Re: How many twoelement subsets of {1,2,3,4} are there that do not [#permalink]
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21 Sep 2017, 14:53
srijatverma wrote: How many twoelement subsets of {1,2,3,4} are there that do not contain the pair of elements 2 and 4?
(a) One (b) Two (c) Four (d) Five (e) Six The number of 2element subsets that can be formed from a 4element set is 4C2 = (4 x 3)/2! = 6. Since the pair of elements 2 and 4 is only 1 of these 6 subsets, we have 6  1 = 5 subsets that do not contain the pair of elements. Answer: D
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Re: How many twoelement subsets of {1,2,3,4} are there that do not [#permalink]
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07 Feb 2018, 12:41
Hi All, You can use the Combination Formula to answer this question, although we have to do a little bit of extra work at the end. Since the number of possible outcomes is so small, you could also list them all out. 4C2 = 4!/(2!2!) = 6 pairs The pairs would be 12, 13, 14, 23, 24 and 34 Since we're asked to NOT use 24, there are 5 options remaining. Final Answer: GMAT assassins aren't born, they're made, Rich
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Re: How many twoelement subsets of {1,2,3,4} are there that do not [#permalink]
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24 Mar 2018, 11:03
srijatverma wrote: How many twoelement subsets of {1,2,3,4} are there that do not contain the pair of elements 2 and 4?
(a) One (b) Two (c) Four (d) Five (e) Six hi, can anyone explain what does subset mean ? I didn't understand the question ...



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Re: How many twoelement subsets of {1,2,3,4} are there that do not [#permalink]
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24 Mar 2018, 11:12
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dave13 wrote: hi, can anyone explain what does subset mean ? I didn't understand the question ... Hey dave13 , Subset means part of the set. Here : Set is {1,2,3,4} Subset could be {1} , {2}, {1,2},{1,2,3}, etc. where {1} is one element subset, {1,2} is two element subset and so on. Question is asking how many such two element subsets could be made. Does that make sense?
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