What is the capacity of a 4-inch pipe that is 18 inches long?

To determine the capacity of a 4-inch pipe that is 18 inches long, it's essential to calculate the volume of the cylinder that the pipe represents. The formula to calculate the volume of a cylinder is:

[ \text{Volume} = \pi r^2 h ]

Where ( r ) is the radius, and ( h ) is the height (or length in the case of a horizontal pipe).

For a 4-inch diameter pipe, the radius ( r ) would be half of the diameter:

[ r = \frac{4 , \text{inches}}{2} = 2 , \text{inches} ]

The length of the pipe ( h ) is 18 inches.

Now substituting these values into the volume formula:

[ Volume = \pi (2 , \text{inches})^2 (18 , \text{inches}) ]

[ Volume = \pi (4 , \text{square inches}) (18 , \text{inches}) ]

[ Volume = \pi (72 , \text{cubic inches}) ]

Now, calculating this gives approximately:

[ Volume \approx 3