Answer
a)
$r$ = $\frac{R(h-y)}{h}$
b)
$V$ = $\frac{\pi{R}^{2}h}{3}$
Work Step by Step
a)
R = radius of cone
h = height of cone
r = radius and height y
$\frac{h}{h-y}$ = $\frac{R}{r}$
$r$ = $\frac{R(h-y)}{h}$
b)
$V$ = $\int_0^h(\frac{R(h-y)}{h})^{2}dy$
$V$ = $\frac{-h\pi}{3R}[\frac{R(h-y)}{h}]^{3}|_0^h$
$V$ = $\frac{\pi{R}^{2}h}{3}$