HI All,
This DS question involves a handful of simple math "rules" and can be solved by TESTing VALUES.
We're told that A and B are positive integers. We're asked for the value of A+B
Fact 1: A/B = 5/8
This gives us the ratio of the two integers, but not the integers themselves. It also means that A is a multiple of 5 and B is the equivalent multiple of 8.
IF....
A = 5
B = 8
Then the answer to the question is 13
IF....
A = 10
B = 16
Then the answer to the question is 26
Fact 1 is INSUFFICIENT
Fact 2: The greatest common divisor of A and B is 1
IF....
A = 1
B = 2
Then the answer to the question is 3
A = 5
B = 8
Then the answer to the question is 13
Fact 2 is INSUFFICIENT
Combined, we know
A/B = 5/8; A is a multiple of 5 and B is the equivalent multiple of 8
The greatest common factor of A and B is 1
IF....
A = 5
B = 8
Then the answer to the question is 13
Since A and B are multiples of 5 and 8, respectively, we can stop working. If we take ANY multiple of the two (then those resulting numbers will have a GCF that is GREATER than 1
For Example....
A = 10
B = 16
These numbers have a CGF of 2. This does not match the "restriction" from Fact 2, so it's NOT a useable TEST. None of the possibilities beyond 5 and 8 will "fit" these restrictions, so the answer to the question MUST be 5+8 = 13
Combined, SUFFICIENT.
Final Answer:
GMAT assassins aren't born, they're made,
Rich
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