Math in the Workplace: Overview

Math in the Workplace - Geometry Problems

Problem:

When an electrician wires a house, the switch boxes must be properly sized.

Each insulated wire (wire size called #14) requires 2.25 cubic inches of space.

Any number of bare wires all together only needs another 2.25 cubic inches of space.

Each cable contains two (2) insulated and one (1) bare wire.

All switch boxes are 2 inches wide and 3.5 inches high, but some come in different depths.

How many cables can be put into a box that is 3 inches deep?

HEWLETT-PACKARD COMPANY

Solution:  

Box volume is 3" x 3.5" x 2" or 21 in³

Space needed for insulated wires:
21 in³ - 2.25 in³ = 18.75 in³
(all bare wires need only 2.25 in³).

Space needed for each cable that contains two insulated wires:
2.25 in³ x 2 = 4.50 in³

Maximum number of cables allowed:
18.75 in³ 4.50 in³ = 4.166…

Therefore, 4 cables can be put into the box.

Math in the Workplace: Overview