Question

A circular patio has a radius of 18 feet.
What is the longest distance across the patio?
A.
9 ft
B.
18 ft
C.
36 ft
D.
54 ft

Answer 1

We have some clues here. 

'longest distance' could mean Diameter. 

r*2= d
radius = 18 feet
18*2 = 36

d = 36

The answer would be: 36 ft 

Answer 2

The longest distance of a circle is its circumference.

Circumference = π d
d = diameter is twice the radius

C = 3.14 * 2 * 18ft
C = 3.14 * 36 ft
C = 113.04 ft

However, with the choices we only need to get the diameter as the longest distance from one end of the circular patio to the other.

d = 2 r
d = 2 * 18ft
d = 36 ft.  CHOICE C.