Rhode Island Journeyman Plumber Practice Exam

Given a 4" pipe that is 150 feet long, how many gallons does it hold?

1. 5 gallons

2. 10 gallons

3. 15 gallons

4. 20 gallons

The correct answer is: 10 gallons

To determine how many gallons a 4" pipe that is 150 feet long holds, you can use the formula for the volume of a cylinder, which is given by: \[ Volume = \pi \times (radius^2) \times height \] In this case, the diameter of the pipe is 4 inches, which means the radius is 2 inches. First, it's essential to convert all measurements to a consistent unit. Since we want to find the volume in gallons, it is most useful to convert inches to feet. 2 inches can be converted to feet as follows: \[ \text{Radius in feet} = \frac{2 \text{ inches}}{12 \text{ inches/foot}} = \frac{1}{6} \text{ feet} \] Now, we plug the radius and length of the pipe (150 feet) into the volume formula: \[ Volume = \pi \times \left(\frac{1}{6}\right)^2 \times 150 \] Calculating the above: 1. Calculate \((\frac{1}{6})^2 = \frac{1}{36}\). 2. Multiply by 150 feet: \[