Question

A regular octagon has side length 10.9 in. The perimeter of the octagon is 87.2 in and the area is 573.67 in2. A second octagon has side lengths equal to 21.8 in. Find the area of the second octagon. Round to the nearest hundredth.

Answer 1

2,294.66 square inches

Explanation:

The area of an octagon is given by the formula:

A = 2 * a² * ( 1 + √2 )

So, if we input the numbers we have:

A = 2 * 21.8² * ( 1 + √2 )

A = 2 * 475.24 * (2.4142)

A = 2,294.66 square inches

As you can see, if you double the side of an octagon, its area will quadruples, which is logic since the one variable in the calculation of the area is the side's length... that is squared. So, if you double it, that double factor is squared.

It's as if we had written

A = 2 * (10.9 * 2)² * ( 1 + √2 )

A = 2 * (10.9² * 2²) * ( 1 + √2 )