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# Each integer from 1 to 50 whose units digit is a 3 is writte

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Kudos [?]: 965 [0], given: 4466

Each integer from 1 to 50 whose units digit is a 3 is writte [#permalink]  22 May 2017, 00:53
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Question Stats:

55% (01:29) correct 44% (01:28) wrong based on 9 sessions

Each integer from 1 to 50 whose units digit is a 3 is written on a slip of paper and placed in a box. If two slips of a paper arc drawn at random without replacement, what is the probability that both the numbers picked are prime?

[Reveal] Spoiler: OA
$$\frac{3}{5}$$

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Kudos [?]: 1039 [1] , given: 6

Re: Each integer from 1 to 50 whose units digit is a 3 is writte [#permalink]  05 Aug 2017, 13:33
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Expert's post
Carcass wrote:

Each integer from 1 to 50 whose units digit is a 3 is written on a slip of paper and placed in a box. If two slips of a paper arc drawn at random without replacement, what is the probability that both the numbers picked are prime?

[Reveal] Spoiler: OA
$$\frac{3}{5}$$

Each integer from 1 to 50 whose units digit is a 3 is written on a slip of paper and placed in a box.
So, the numbers in the box are: 3, 13, 23, 33, and 43 (5 numbers)
Among those 5 numbers, the primes are: 3, 13, 23, and 43 (4 numbers)

P(both are prime) = P(1st number is prime AND 2nd number is prime)
= P(1st number is prime) x P(2nd number is prime)
= 4/5 x 3/4
= 3/5

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Re: Each integer from 1 to 50 whose units digit is a 3 is writte   [#permalink] 05 Aug 2017, 13:33
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