BTGModeratorVI wrote: ↑Mon Dec 28, 2020 8:36 am
Is ab a prime number?
(1) a is a prime number.
(2) b is not a prime number.
Answer:
E
Source: Veritas Prep
Kudos for a correct solution.[/quote]
Target question: Is ab a prime number?
Statement 1: a is a prime number
This statement doesn't FEEL sufficient, so I'll TEST some values.
There are several scenarios that satisfy statement 1. Here are two:
Case a: a = 2 and b = 1 , in which case
ab = 2, and 2 IS prime
Case b: a = 2 and b = 6 , in which case
ab = 12, and 12 in NOT prime
Since we cannot answer the
target question with certainty, statement 1 is NOT SUFFICIENT
Aside: For more on this idea of plugging in values when a statement doesn't feel sufficient, you can read my article: https://www.gmatprepnow.com/articles/dat ... lug-values
Statement 2: b is not a prime number
This statement doesn't FEEL sufficient, so I'll TEST some values.
There are several scenarios that satisfy statement 2. Here are two:
Case a: a = 2 and b = 1 , in which case
ab = 2, and 2 IS prime
Case b: a = 2 and b = 6 , in which case
ab = 12, and 12 in NOT prime
Since we cannot answer the
target question with certainty, statement 2 is NOT SUFFICIENT
Statements 1 and 2 combined
There are still several possible scenarios that meet both statements. Here are two:
Case a: a = 2 and b = 1 , in which case
ab = 2, and 2 IS prime
Case b: a = 2 and b = 6 , in which case
ab = 12, and 12 in NOT prime
Since we cannot answer the
target question with certainty, the combined statements are NOT SUFFICIENT
Answer = E
Cheers,
Brent
