topspin20 wrote:Is (a/b)>(3/5)?
1) (a+1/b)>(3/5)
2) (a/b+1)>(3/5)
Answer: B
Given a/b > 3/5, we can rephrase the question stem as 5a > 3b ONLY IF THE PROBLEM IS RESTRICTED TO POSITIVE VALUES.
Here, it's possible that b<0, in which case statement 2 is NOT sufficient.
Statement 2: a/(b+1) > 3/5
Case 1: a=4 and b=3
The constraint that a/(b+1) > 3/5 is satisfied:
a/(b+1) = 4/(3+1) = 4/4 = 1.
In this case, a/b = 4/3, so a/b > 3/5.
Case 2: a=0.5 and b=-0.5
The constraint that a/(b+1) > 3/5 is satisfied:
a/(b+1) = 0.5/(-0.5+1) = 0.5/0.5 = 1.
In this case, a/b = 0.5/-0.5 = -1, so a/b < 3/5.
INSUFFICIENT.
Note the following:
In Case 2, a/b < 3/5, but 5a > 3b.
This illustrates why -- if the signs of a and b are unknown -- it's best not to rephrase a/b > 3/5 as 5a > 3b.
If the problem has been posted correctly, the OA should not be
B.
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