2x + 1 is a prime number between 30 and 50. Is x + 2 prime?
(1) x is odd
(2) x is divisible by 3
GMAT DS Question of the Day based on Prime Number
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31,37,41,43,47 are the prime numbers for which ‘x’ can be 15,18,20,21,23 respectively (for expression 2x+1). With these results x+2 becomes 17,20,22,23,25 respectively. Now
by (1) if x is odd then we have 15,21 and 23 and x+2 as 17,23 and 25
and by (2) if x is div by 3 then we have 15,18 and 21 and x+2 as 17,20 and 23. By combining both the statements we have x+2 as 17 and 23.
Hence by combining both the statements we can say that x+2 is prime number.
Since x+ 2 is not always prime ans should be cannot be determined
@Nitin Sharma
Excellent Explanation & right answer.
Option C implies both statement together can furnish unique solution
E. Neither 1 or 2 is sufficient to answer the question, and more information is required…
C
E
D
Both combined give the ans……..