Chapter 12 - Section 12.6 - Elasticity - Exercises - Page 931: 3b

$p=\$33.33$

The elasticity of the demand function is: $E=-(-2(100-p))\times\frac{p}{(100-p)^2}$ If we want to maximize the revenue, then, $E=1$. If the demand function is $q=(100-p)^2$ and $p=\$30$ $E=-(-2(100-p))\times\frac{p}{(100-p)^2}=1$ $(200-2p)\times p=(100-p)^2$ $2p=100-p$ $p=\$33.33$