Science and Mathematics for Engineering 6th Edition by John Bird

Exercise 18

An approximate relationship between the number of teeth $\mathrm { T }$ on a milling cutter, the diameter of the cutter $D$ and the depth of cut $d$ is given by: $T = \frac { 12.5 D } { D + 4 d }$
Evaluate $\mathrm { d }$ when $\mathrm { T } = 10$ and $\mathrm { D } = 32$ .