SOLUTION: A garden path around a circular garden is 5 feet wide all they way around and the distance around the outside of the garden path is 80 feet. If a bag of gravel will cover an area

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Question 858989: A garden path around a circular garden is 5 feet wide all they way around and the distance around the outside of the garden path is 80 feet. If a bag of gravel will cover an area of 10 square feet, how many bags of gravel will the gardener need to cover the path? Explain
Answer by mananth(16946) About Me  (Show Source):
You can put this solution on YOUR website!
Diameter including walkway = 80 feet
so radius = 40 feet
the width is 5 feet
so the garden radius = 35 feet
Area of walkway = total area - garden area
Total area = pi*r^2
=pi*40^2
garden area = pi*35^2
Difference = pi*40^2-pi^35^2
=pi(40^2-30^2)
= 121 sq.ft

10 sq.ft ----------------1 bag
121 sq.ft ---------------?
121/10
=12.1 bags
= 13 bags of gravel