If p is a positive integer, is 2p + 1 prime?
(1) p is prime
(2) units digit of p is not prime
OA E
Source: Official Guide
If p is a positive integer, is 2p + 1 prime?
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Statements combined:BTGmoderatorDC wrote:If p is a positive integer, is 2p + 1 prime?
(1) p is prime
(2) units digit of p is not prime
OA E
Source: Official Guide
Case 1: p=11 --> p is prime, but its units digits is not prime
In this case, 2p+1 = 2*11 + 1 = 23.
Since 23 is prime, the answer to the question stem is YES.
Case 2: p=19 --> p is prime, but its units digit is not prime
In this case, 2p+1 = 2*19 + 1 = 39.
Since 39 is not prime, the answer to the question stem is NO.
Since the answer is YES in Case 1 but NO in Case 2, the two statements combined are INSUFFICIENT.
The correct answer is E.
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Followed here and elsewhere by over 1900 test-takers.
I have worked with students based in the US, Australia, Taiwan, China, Tajikistan, Kuwait, Saudi Arabia -- a long list of countries.
My students have been admitted to HBS, CBS, Tuck, Yale, Stern, Fuqua -- a long list of top programs.
As a tutor, I don't simply teach you how I would approach problems.
I unlock the best way for YOU to solve problems.
For more information, please email me (Mitch Hunt) at [email protected].
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