Real-Life Math -- Solution
The first step in solving this type of question is to illustrate it.
This graphic shows an illustration of the "tube."
The tube resembles a cylinder, as you can see.
The next step is to calculate its volume using the following formula:
We already know the value of pi equals 3.14. As for r, it is half of the diameter. So it equals 6 inches. And as for h, it is 4 feet or 48 inches.
Volume = 3.14 x 62 x 48
Volume = 5,425.92 cubic inches
So you need 5,425.92 cubic inches for 1 tube. So for 4, you would need 21,703.68 cubic inches of concrete.
Now you just need to convert that figure into cubic feet.
Since 1 cubic foot has a value of 1,728 cubic inches -- 12 x 12 x 12 -- you just have to divide 21,714.68 by 1,728.
The final answer is 12.57 cubic feet.