Hi guerrero,
In these types of questions, you can use a math tactic called "prime factorization"
Here, we're told that z is a multiple of 9, so that means it has these factors:
z = (3)(3)(possibly other primes)
We're also told that w is a multiple of 4, so that means it has these factors:
w = (2)(2)(possibly other primes)
The question asks if zw is a multiple of 126? This is another way of asking if zw is made up of (2)(3)(3)(7)(possibly other primes)?
Since we have a 2 from the w and both 3s from the z, we really just need to know if we can find a 7 or not (this is what's referred to as "the question behind the question).
Fact 1 tells us that z is a multiple of 21. This means that, in addition to the (3)(3), z also has a 7
This is enough to confirm that zw is a multipole of 126.
Fact 1 is SUFFICIENT
Fact 2 tells us that w is a multiple of 25. This means that, in addition to the (2)(2), z also has (5)(5). MAYBE it has a 7, MAYBE it doesn't
Fact 2 is INSUFFICIENT
Final Answer: A
GMAT assassins aren't born, they're made,
Rich
If z is a multiple of 9 and w is a multiple
This topic has expert replies
Source: Beat The GMAT — Data Sufficiency |
GMAT/MBA Expert
-
[email protected]
- Elite Legendary Member
- Posts: 10392
- Joined: Sun Jun 23, 2013 6:38 pm
- Location: Palo Alto, CA
- Thanked: 2867 times
- Followed by:511 members
- GMAT Score:800
