tamiri wrote:
If positive integers A and B have LCM of 150, what is their possible GCD?
a. 3
b. 7
c. 9
d. 20
e. 45
Here's another approach.
For GCD and LCM questions, it's useful to be able to think of pairs of values that have given GCDs or LCM's.
So, if we're told that A and B have a LCM of 150, what are some possible values of A and B?
Here are a few:
A = 150 and B = 150
A = 150 and B = 1
A = 150 and B = 10
etc.
Let's keep listing possibilities, and see if any have a GCD that matches one of the answer choices.
A = 150 and B = 150
GCD = 150
Not one of the answer choices. Keep trying.
A = 150 and B = 1
GCD = 1
Not one of the answer choices. Keep trying.
A = 150 and B = 2
GCD = 2
Not one of the answer choices. Keep trying.
A = 150 and B = 3
GCD = 3
YES, one of the answer choices.
Answer =
A
Cheers,
Brent
Brent Hanneson - Creator of GMATPrepNow.com
