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. $1,714.07
B. $1,247.08
C. $276.40
D. $1,174.70

Answer 1

$1,174.70

Explanation:

Given : A circular pool with a diameter of 18 ft will have a uniform 4 ft concrete walkway poured around it.

To Find: If the concrete cost $4.25 a square foot, how much will it cost for the concrete?

Solution:

A circular pool has diameter of 18 ft will have a uniform 4 ft concrete walkway around it.

So radius = diameter /2 =18/2 =9 feet

Thus Area of circular pool =
`\pi r^(2)` =
`\pi 9^(2)`

Use π =3.14

Thus Area of circular pool =
`3.14*9^(2)`

=
`3.14*81`

= 254 . 37 square feet

Since the Radius of the pool with concrete = 9 + 4= 13

So, Area of circular pool with concrete=
`3.14*13^(2)`

=
`3.14*169`

= 530.66 square feet

Now surface area of concrete = area of pool with concrete - area of pool

Surface area of concrete= 530.66 - 254.34 = 276.32 square feet

If the concrete cost $4.25 a square foot of surface area,

So the cost for the concrete of 276.32 square feet = 276.32 * 4.25 = $ 1174.36

The option close to our answer is $1,174.70

Thus Option D is correct

Answer 2

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?

This can be solve be solving the area of walkway

Area of walkway is equal to = (pi)( 9 ft +4) ^2– (pi)(9ft)^2

= 276.46 sq ft

Cost = 276.46 sq ft * ($4.25 a square foot) = $1174.70