avggmatstudent23
If \(\frac{-1}{2}\leq x \leq\frac{-1}{9}\) and \(\frac{-1}{4}\leq y \leq\frac{1}{25}\), what is the maximum value of \(xy^2\)
(A) \(\frac{-1}{16}\)
(B) \(\frac{-1}{32}\)
(C) \(\frac{-1}{144}\)
(D) \(\frac{-1}{5625}\)
(E) 0
I get the correct answer when I first square the y inequality and then multiply it by the x inequality i.e. \(y^2 * x\). However, I get the wrong answer when I first multiply the x and y inequalities and then multiply the y inequality again i.e. \(xy * y\).
What am I missing here?
Bunuel chetan2uSource: GMATClub video with Crackverbal (see at 50:00 mark)
Hello
I hope you're well.
Do not stress. I believe that you're simply overthinking your approach.
Multiplying any three values should give you the same result; you may perform the operation in any order.
Options A till D are all negative, and only option E is 0 (non-negative).
0 is the largest of all the options.
The range of X does not cross the number line from negative to positive; however, the range of Y does so.
X will always be negative.
Y^2 will always be non-negative.
Multiplying X and Y^2, you will always get a negative output except when Y is 0.
I already know that I get the right answer by multiplying x with y^2. My question is why don't I get the correct answer if I multiple xy with y.
Why don't you try solving it this way and let me know if you figure out where I'm going wrong.