Question

Mr. Murphy is designing a rectangular concrete fire pit. The concrete sides and bottom will be 5 inches thick. The interior length will be 3 times the interior

height and the interior width will be 2 times the interior height. What should the outer dimensions of the fire pit be if the inner volume is to be 6000 cubic
inches?
Enter the correct values in the boxes.

*15 is correct but 25 & 35 are wrong ..*

Answer 1

For the outer dimensions: length = 35 inches, width = 25 inches, and height = 15 inches.

Explanation:

For the interior;

volume = 6000

length, l = 3h

width, w = 2h

height = h

But,

Volume of a cuboid = length x width x height

So that;

6000 = 3h x 2h x h

6000 = 6

Divide through by 6 to have;

1000 =

h =

= 10

Thus, the height is 10 inches. Thus;

length, l = 3h = 3 x 10 = 30 inches

width, w = 2h = 2 x 10 = 20 inches

For the outer dimension, since the concrete sides and bottom would be 5 inches thick. Then its dimension are;

length, l = 30 + 5 = 35 inches

width, w = 20 + 5 = 25 inches

height = 10 + 5 = 15 inches