MGMAT Test Question

[suryakant.ankolekar]

Hello,

I came across a equation question in MGMAT test.

What is the value of y?

(1) 3|x2 - 4| = y - 2 ->> x square

(2) |3 - y| = 11

answer is given as 'C', stating that Statement (1) tells us that y is greater than or equal to 2.
I am not convinced by this answer.

if i substitue X by 1 in st 1, it gives me value of Y as -9 or 9.
Hence i feel the answer of this question must be E.

[atul.prasad]

Hi Suryakant,

statement 1 establishes that y HAS TO BE >= 2 since Left hand side of the equation cannot be negative

from 2 we have y = 14 or y = -8 (so we cannot choose)

on combining 1 and 2 , we get C as the answer.

"if i substitue X by 1 in st 1, it gives me value of Y as -9 or 9.
Hence i feel the answer of this question must be E."

How did you arrive at this? The left hand side of the equation cannot be evaluated to a negative value. So y has to be +ve and >2

[suryakant.ankolekar]

Hi Atul,

Thanks.
I interpreted this question in another way.

whenever we read |X|, it means that X could be -X or +X.
so here i tried deriving the actual value of |X^2 - 4|, leading to two different values. viz. when X was 1, left side eq became 3 (1 -4) and 3 * (-1X + 4).

Rgds,
Surya

[atul.prasad]

I understand Surya,

| | is a confusing operator. Nevertheless, my advice is that whenever you see this, be sure to check back your results by putting it into the equation. That reduces the possibility of errors.

Good Luck!

[jnelson0612]

Nice explanation atul.

Going forward, please post CAT math questions into this forum: gmat-prep-math-f30.html

This forum is more appropriate for general math questions.

Thank you!