Chapter 11, Problem 22CPS

C. Practical Applications.

For each of the following, set up either a system of equations in two variables or a quadratic equation and solve. (Round to two decimal places if necessary.)

Construction The section modulus 5 of a beam in cubic inches is given by the formula

$S\text{}=\frac{b{d}^2}{6}$

where b and d are the breadth and depth of the beam in inches.

Find the depth of a beam if its breadth is $3\frac{7}{8}$ in. and the section modulus is 7.25 in.³. (Round to the nearest eighth of an inch.)