Question

A square of the sides are decreasing by 20% .what is the net change of area?

Answer 1

The net change of area is a decrease of `36%`

Explanation:

Let's say the original square has sides of length `x`. Therefore, it will have an area of `x*x`, or `x^2`.
Now, we know that our new square's sides are decreasing by 20%. This will result in a length 80% of the original square, because `20%+80%=100%`. So, we can state the area of the new square as `(80%*x)(80%*x)`, or more simply `0.8x*0.8x`. By combining like terms, we can simplify this equation to `0.64x^2`. Therefore, the net change in area is a decrease of `100%-64%`, or `36%` using the same form as the question.