LUANDATO wrote:Is ab < 9 ?
(1) a<2 and b<4
(2) 1/5 < a < 3/4 and b^2 < 121
The OA is B.
I don't have it clear. Can any expert explain this DS question please? Thanks.
(1) a < 2 and b < 4
Case 1: Say a = 0 and b = 0, then ab= 0. The answer is yes.
Case 2: Say a = -3 and b = -3, then ab= 9. The answer is No.
No unique answer. Insufficient.
(2) 1/5 < a < 3/4 and b^2 < 121
=> a is positive and -11 < b < 11. Thus, b can be negative, 0 or positive
Case 1: If b is negative, then ab = a negative number. The answer is yes.
Case 2: If b is 0, then ab = 0. The answer is yes.
Case 3: Let's take the maximum possible values of a and b. Thus, ab < (3/4)*(11) => ab < 33/4 => ab < 8.25. The answer is yes. Sufficient.
The correct answer:
B
Hope this helps!
-Jay
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