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# A is a member of a set of numbers {2, 3, 24, 50 and 178}.

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Moderator
Joined: 18 Apr 2015
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Kudos [?]: 1033 [0], given: 4655

A is a member of a set of numbers {2, 3, 24, 50 and 178}. [#permalink]  05 May 2018, 07:22
Expert's post
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Question Stats:

27% (01:15) correct 72% (01:30) wrong based on 11 sessions
A is a member of a set of numbers {2, 3, 24, 50 and 178}. If $$N= 6^A$$ , what is the probability that 876,463 is not a multiple of $$N$$ ?

A. 0%

B. 6%

C. 40%

D. 78%

E. 100%
[Reveal] Spoiler: OA

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Intern
Joined: 10 Apr 2018
Posts: 17
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Kudos [?]: 10 [1] , given: 28

Re: A is a member of a set of numbers {2, 3, 24, 50 and 178}. [#permalink]  05 May 2018, 07:39
1
KUDOS
this is how I solved it:

876,463 is only divisible by 7; it can't be divided by 6.
since N is a multiple of 6, so 876,463 has to be divisible by 6. BUT we already know that it can't be. So there's no way 876,463 can be a multiple of N.
so the answer would be 100% (876,463 must not a multiple of N)

unfortunately I miss the word "not" in the question prompt so I clicked the wrong option (I clicked the choice 0% instead)
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Joined: 27 Feb 2017
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Kudos [?]: 45 [1] , given: 15

Re: A is a member of a set of numbers {2, 3, 24, 50 and 178}. [#permalink]  05 May 2018, 10:55
1
KUDOS
Okay, I will admit that this question looks too hard to be simple. Which means, I did think that 876,463 should be divisble by 6 for it to be a multiple of N. But the I thought they wouldne give all this information for just one step and I was stumped. Took me 4 mins to find a way and I still got the wrong answer
Moderator
Joined: 18 Apr 2015
Posts: 5166
Followers: 77

Kudos [?]: 1033 [0], given: 4655

Re: A is a member of a set of numbers {2, 3, 24, 50 and 178}. [#permalink]  05 May 2018, 15:23
Expert's post
Remember always this : GRE is a test NOT of calculation but rather to think critically and to find the best and easy way to solve a question.

Now, we said that $$N= 6^A$$, which is basically $$(2*3)^A$$.

In this scenario, our number 876,463 is odd because it ends with 3 and never can be a multiple of $$6^A$$ that contains also the 2.

what is the probability that 876,463 is not a multiple of $$N$$?

Our answer is 100% because we are sure that that number will be never a multiple of $$6^A$$.

PS: notice that the first answer is impossible. A probability can never be 0%. It is always between 0 and at most 1.

Hope this helps
_________________
Re: A is a member of a set of numbers {2, 3, 24, 50 and 178}.   [#permalink] 05 May 2018, 15:23
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