__Category__: Solid Geometry"Published in Vacaville, California, USA"

Compute the cost of the lumber necessary to resurface a foot-bridge 16 ft. wide, 150 ft. long with 2-in. planks, if lumber is $40 per 1000 board feet. Neglect waste. (One board foot = 1 ft. by 1 ft. by 1 in.)

__Solution__:

To illustrate the problem, it is better to draw the figure as follows

Photo by Math Principles in Everyday Life |

The volume of a rectangular parallelepiped is given by the formula

Substitute the values of length, width, and height of a lumber to resurface a foot-bridge, we have

Therefore, the cost of the lumber necessary to resurface a foot-bridge is