SOLUTION: If I have a hole that is 20 inches deep an 7 inches in Dia, how many bags of 40 lbs quickcrete will it take to fill 8 holes?

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Question 356766: If I have a hole that is 20 inches deep an 7 inches in Dia, how many bags of 40 lbs quickcrete will it take to fill 8 holes?
Answer by Fombitz(32388) About Me  (Show Source):
You can put this solution on YOUR website!
First find the volume of each hole which can be modeled as a cylinder with a 7" diameter and 20" height.
V%5Bc%5D=pi%2AR%5E2%2AH
V%5Bc%5D=pi%2A%283.5%29%5E2%2A20
V%5Bc%5D=245%2Api or approximately
V%5Bc%5D=770 cubic inches
For 8 holes,
V%5B8c%5D=6158 cubic inches.
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From the Quikrete 5000 spec sheet, each 80 lb bag provides 0.60 cubic feet.
Convert to cubic inches (12 inches/foot)^3.
V%5Bbag%5D=0.60%2812%5E3%29=1036.8 cubic inches
So then,
N=V%5B8c%5D%2FV%5Bbag%5D=6158%2F1036.8=5.94bags
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If this is a math problem, round up to 6 bags.
If this is a project, buy 10% more, get 7 bags.