Step-by-step explanation:
[tex]v \: = \: \pi \: {r}^{2} \times \frac{h}{3} [/tex]
rearrange to get
[tex]48\pi \: = \: \pi {r}^{2} \times \frac{9}{3} [/tex]
remove pi from both sides
[tex]48 \: = {r}^{2} \: \times 3[/tex]
[tex] \frac{48}{3} = {r}^{2} [/tex]
[tex]16 = {r}^{2} [/tex]
[tex]r = \sqrt{16} [/tex]
[tex]r = 4[/tex]
