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# If a is the smallest prime number greater than 21 and b is t

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If a is the smallest prime number greater than 21 and b is t [#permalink]  06 Mar 2018, 15:19
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Question Stats:

100% (00:35) correct 0% (00:00) wrong based on 10 sessions
If a is the smallest prime number greater than 21 and b is the largest prime number less than 16, then ab =

A 299
B 323
C 330
D 345
E 351

kudos for the right explanation and solution
[Reveal] Spoiler: OA

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Re: If a is the smallest prime number greater than 21 and b is t [#permalink]  06 Mar 2018, 20:42
1
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The next prime above 21 is 23, since 22 is even. So a is 23.

The greatest prime less than 16 is 13, so b is 13.

Rather than multiply 13 and 23, notice that if you did, the units digit of the number will be 9, since 3x3 is 9. Since A is the only answer ending in 9, the answer must be A.
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Re: If a is the smallest prime number greater than 21 and b is t [#permalink]  29 May 2018, 14:58
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Carcass wrote:
If a is the smallest prime number greater than 21 and b is the largest prime number less than 16, then ab =

A 299
B 323
C 330
D 345
E 351

The smallest prime number greater than 21 is 23. The largest prime number less than 16 is 13.

Thus, a x b = 23 x 13 = 299.

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Re: If a is the smallest prime number greater than 21 and b is t   [#permalink] 29 May 2018, 14:58
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