GMAT Math : Data Sufficiency

GMAT Math : Data Sufficiency 

 Question

 How must is 60 percent of a certain number

Statement 1 : 25 percent of twice the number is equal to half the number.
Statement 2 : 50 percent of the number is 20 less than the number.

A) If statement 1 alone is sufficient to answer the question, but statement 2 alone is not sufficient.
(B) If statement 2 alone is sufficient to answer the question, but statement 1 alone is not sufficient.
(C) If both statements together are needed to answer the question, but neither statement alone is sufficient.
(D) If either statement by itself is sufficient to answer the question.
(E) If not enough facts are given to answer the question.

Solution:

 Answer B

Evaluating Statement 1: 25 percent of twice the number is equal to half the number.

 To determine what is 60 of a certain number (say x), you need to know what the value of that number (x) is. Statement 1 seems to provide that equation to solve for the value of x, but when you read this statement closely it is bogus leads you nowhere.

it states as
2 (0.25x ) = 0.5x
0.5x = 0.5x

You cannot solve for the value of x.

 Evaluating Statement 2: 50 percent of the number is 20 less than the number. 

 The Equation for this statement will be

0.5x = x-20
This implies,
x-0.5x= 20
Solving for 
0.5x =20
x=40

Since we know the value of X we can now find 60 percent of x.
So the correct choice is answer B