if you had a 3inch pipe, 20 feet long, full of water how many gallons of water would be in this pipe

Question

I want to solve this math problem if you had a 3inch pipe, 20 feet long, full of water how many gallons of water would be in this pipe

Answer 1

V = πr²h

V = π(1.5)²(240)               20 feet = 240 inches

V = π(2.25)(240)

V = π(540)

V ≈ 1696

 

The volume of the pipe is approximately 1696 in³.

One gallon is 231.001 in³.

 

1696 / 231.001 ≈ 7.34

 

The pipe holds approximately 7.34 gallons.

Answer 2

In the end, you need a conversion factor to get you from volume in either cubic inches or cubic feet (your choice, but you have to be consistent on the units) to volume in gallons. That need for a conversion factor may be a swerve put into the problem to try to throw you off. Watch out!

 

So. OK. The pipe is a cylinder. Its volume is πr²h, where

 

r = radius

h = height if the pipe is vertical (or length if the pipe is horizontal)

 

In this case r = 1.5 inches and h = 20 feet (which is 240 inches). So the volume is 1696 cubic inches. (I would round it up to 1700.)

 

1 cubic inch is 0.00432899 gallons. (That's your conversion factor, 0.004329 gal/in³.) So 1700 cubic inches is 7.34 gallons. Cheers!