Hi everyone,
Here is an example I stumbled across quite recently:
If X^3*Y = 24, what is the value of (X^3*Y^3 - X^2*Y^2)?
(1) X^2*Y^2 = 36.
(2) X^3*Y^2 = 72.
The answer page says the correct one is B. However, the statement(1) is also sufficient, since:
X^2*Y^2 = 36 => X*Y = +-6, but if X^3*Y is positive, X*Y can only be positive.
Therefore, X^2*Y^2(X*Y-1)=36(X*Y-1)=36*5 = 180
Please correct me if I'm wrong.
Here is an example I stumbled across quite recently:
If X^3*Y = 24, what is the value of (X^3*Y^3 - X^2*Y^2)?
(1) X^2*Y^2 = 36.
(2) X^3*Y^2 = 72.
The answer page says the correct one is B. However, the statement(1) is also sufficient, since:
X^2*Y^2 = 36 => X*Y = +-6, but if X^3*Y is positive, X*Y can only be positive.
Therefore, X^2*Y^2(X*Y-1)=36(X*Y-1)=36*5 = 180
Please correct me if I'm wrong.
