gmat620 wrote:

Is M < 0 ?

1. - M = | - M |

2. M^2 = 9

Hello Friends, I think mod is always positive, please help me out on this one...This question isn't tough but concept is required. I am little bit confused. Please help me. Thanks in advance.

Question Stem : Is M < 0 ?

St. (1) : (-M) = |(-M)|

Now, |-M| basically means this :

(a) When (-M) > 0, |(-M)| = (-M)

(b) When (-M) < 0, |(-M)| = -(-M)

Thus, for statement 1 to be valid, it would seem that (-M) must be greater than 0 which means M must be less than 0.

However, the value of M = 0 also satisfies this statement. Thus M <= 0.

Hence Statement is Insufficient.

St. (2) : M^2 = 9

This means that M = ±3

Therefore M can be positive or negative.

Statement Insufficient.

St. (1) and (2) together : M <= 0 , M = ± 3

The only value that satisfies both statements is - 3.

Thus we can conclude that M < 0.

Hence Sufficient.

Answer : C
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