Question

An architect increases the radius of a circle window by 20 percent. By what percent

did the area of the circle window increase?

Answer 1

Explanation:

For a circle of radius R, the area is written as:

A = pi*R^2

Where pi = 3.14

If we increase the radius by 20%, the new radius will be:

R´ = R + 0.20*R = 1.20*R

The new area will be:

A´ = pi*(1.20*R)^2 = (1.20)^2*pi*R^2

= 1.44*pi*R^2

And pi*R^2 = A, the original area, then_

A´ = 1.44*A = A + 0.44*A

This means that the percentage in which the area increased is:

0.44*100% = 44%

Answer 2

Answer: 44%

Explanation:

For a circle of radius R, the area is written as:

A = pi*R^2

Where pi = 3.14

If we increase the radius by 20%, the new radius will be:

R´ = R + 0.20*R = 1.20*R

The new area will be:

A´ = pi*(1.20*R)^2 = (1.20)^2*pi*R^2

= 1.44*pi*R^2

And pi*R^2 = A, the original area, then_

A´ = 1.44*A = A + 0.44*A

This means that the percentage in which the area increased is:

0.44*100% = 44%