Carcass wrote:
The length of a rectangle is increased by 25%. By what percentage should the width be decreased so that the area of the rectangle remains unchanged?
(A) 20
(B) 25
(C) 30
(D) 33.33
(E) 50
We can let the original length = 4, and the original width = 10.
So the original area is 40.
When the length increases by 25% we have 4 x 1.25 = 5
Thus, for the area to remain 40, the width must be 8.
Since (8 - 10)/10 x 100 = -20, we see that 8 is 20 percent less than 10. In other words, the width has to decrease by 20%.
Answer: A