Question

A circular pool with a diameter of 18 ft will have a uniform 4 ft concrete walkway poured around it. If the concrete cost $4.25 a square foot, how much will it cost for the concrete?
A. $1,247.08
B. $1,174.70
C. $1,714.07
D. $276.40

Answer 1

Diameter = 18 ft.
Radius = 18/2 = 9 ft.

Area for walkway around the circular pool =
Area of R (R = 9+4 ft.) - Area of Pool (r = 9 ft.)

πR² - πr²
π(R²-r²)
π(13²-9²)
π(169-81)
π(88)

Now,
1 sq. foot = $ 4.25
π(88) sq. foot = $\frac{22}{7} \times 88 \times 4.25 = 1175.42$

So, Answer will be B. $1174.70 because of the closeness to our answer.