SOLUTION: The diameter of a circular fountain in a city parks 28 feet. A sidewalk that is 3.5 will be built around the fountain. 1. Find the area of the sidewalk rounded to the nearest t

Algebra ->  Circles -> SOLUTION: The diameter of a circular fountain in a city parks 28 feet. A sidewalk that is 3.5 will be built around the fountain. 1. Find the area of the sidewalk rounded to the nearest t      Log On


   

Question 1156839: The diameter of a circular fountain in a city parks 28 feet. A sidewalk that is 3.5 will be built around the fountain.
1. Find the area of the sidewalk rounded to the nearest tenth.
2. 0.8 bag of concrete will be needed for every square foot of the new sidewalk. What is the minimum number of bags needed?
Found 2 solutions by josgarithmetic, ikleyn:
Answer by josgarithmetic(39620) About Me  (Show Source):
You can put this solution on YOUR website!
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The diameter of a circular fountain in a city parks 28 feet. A sidewalk that is 3.5 will be built around the fountain.
1. Find the area of the sidewalk rounded to the nearest tenth.
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Sidewalk, 3.5 feet in width?

pi%2814%2B3.5%29%5E2-pi%2A14%5E2
pi%2A17.5%5E2-pi%2A196
pi%2A%2817.5%5E2-196%29
110.25pisquarefeet

Answer by ikleyn(52802) About Me  (Show Source):
You can put this solution on YOUR website!
.

The area of the circular fountain is pi%2Ar%5E2 = 3.14%2A14%5E2 = 615.44 square feet.


As you understand, 14 here is the radius of the fountain.


The radius of the outer circle is 14+3.5 = 17.5 feet, and the area of that circle is  pi%2A17.5%5E2 = 961.625 square feet.


The difference  961.625 - 615.44 = 346.185 square feet is the area of the sidewalk.


To find the number of bags of concrete, multiply this area by the number 0.8


    N = 346.185*0.8 = 432.7 = 276.9 = 270 bags of concrete  (rounded to the next greater integer).    ANSWER

Solved.

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