Question

A building engineer analyzes a concrete column with a circular cross section. The circumference of the column is 18pi meters. What is the area A of the cross section of the column?

Answer 1

Answer

Circumference(C) of a circle is given by:

$C = 2\pi r$

where r is the radius and value of $\pi = 3.14$

As per the given statement:

A building engineer analyzes a concrete column with a circular cross section.

The circumference of the column is $18 \pi$ meters.

then;

$18 \pi= 2\pi r$

Divide both sides by $2 \pi$ we have;

9 = r

or

r = 9 meters

We have to find the area of the cross section of the column

Area of a circle is given by:

$A = \pi r^2$

then;

$A = \pi \cdot 9^2 = 81 \pi$ meter square.

therefore, the area A of the cross section of the column is $81 \pi$ meter square.

Answer 2

Check the picture below