BREAKING: Target Test Prep releases Brand New 2026 On Demand GMAT prep course

Redeem

Problem 14 Section 11 of 100DS

Expert replies
by isisalaska » Thu Jan 25, 2007 3:44 pm
If a and b are positive integers, is a/b=2/3?

(1) 3a = 2b
(2) For integers m and n, a = 2m and b = 3n

Is not D the the answer? if you substitute 2m by a and 3n by b the result is m=n.
Isis Alaska
Join the discussion
Source: — Data Sufficiency |

by Stacey Koprince » Wed Jan 31, 2007 5:08 pm
yes/no: is a/b = 2/3

(1) 3a = 2b. Can be rearranged to a/b = 2/3. Yes.

(2) a = 2m, b = 3n, m and n are integers. So a/b = 2m/3n. We don't know what m and n are; we only know they are integers.

Nor do we know that m = n; we can't just substitute into the equation given in the question stem b/c we don't know that that equation is true - the point is that we're being asked to determine whether it is true. m could equal n IF that equation is true (that is, if a/b = 2/3 is true). But if it isn't true, then m and n can be any integers. So can't tell for sure.

Answer is A.
Please note: I do not use the Private Messaging system! I will not see any PMs that you send to me!!

Stacey Koprince
GMAT Instructor
Director of Online Community
Manhattan GMAT

Contributor to Beat The GMAT!

Learn more about me
Join the discussion

by Cybermusings » Wed Mar 28, 2007 5:15 am
If a and b are positive integers, is a/b=2/3?

(1) 3a = 2b
(2) For integers m and n, a = 2m and b = 3n

3a = 2b

Thus a/b = 2/3

Hence I is sufficient

a = 2m and b = 3n

Thus a/ b = 2m/3n

But here a/b will be equal to 2/3 if m = n

Hence it may or may not be true

Hence II is insufficient

Thus A
Join the discussion