Max@Math Revolution wrote:[GMAT math practice question]
If m and n are prime numbers, what is the value of m+n?
1) 15 ≤ m < n ≤ 20
2) mn = 323
Given: m and n are prime numbers
Target question: What is the value of m+n?
Statement 1: 15 ≤ m < n ≤ 20
17 and 19 are the only PRIME numbers from 15 to 20 inclusive
So, it must be the case that m = 17 and n = 19
So, the answer to the target question is
m+n = 17 + 19 = 33
Since we can answer the
target question with certainty, statement 1 is SUFFICIENT
Statement 2: mn = 323
Find the prime factorization of 323 to get: 323 = (17)(19)
So, there are two possible cases:
Case a: m = 17 and n = 19,in which case, the answer to the target question is
m + n = 17 + 19 = 33
Case b: m = 19 and n = 17,in which case, the answer to the target question is
m + n = 19 + 17 = 33
In both cases, the answer to the target question is the same:
m + n = 33
Since we can answer the
target question with certainty, statement 2 is SUFFICIENT
Answer: D
Cheers,
Brent
Brent Hanneson - Creator of GMATPrepNow.com
