Answer:
x = 20%
Step-by-step explanation:
The area is the product of side lengths. If the original side is "a", then the one increased by 25% is ...
a + 0.25·a = 1.25a
The one decreased by x is ...
a -x·a = a(1 -x)
We want the area of the square to be the same as that of the rectangle, so we write an equation that says that, then solve for x.
square area = rectangle area
a^2 = (1.25a)(a)(1-x)
1 = 1.25 -1.25x . . . . divide by a^2, eliminate parentheses
1.25x = 0.25 . . . . . add 1.25x -1
x = 0.25/1.25 = 0.20
x = 20% . . . . . . expressed as a percentage
