Answer:
Step-by-step explanation:
Multiply by the inverse of the coefficient of r², then take the square root.
[tex]V=\dfrac{1}{3}\pi r^2h\\\\V=\dfrac{\pi h}{3}r^2\\\\r^2=\dfrac{3V}{\pi h}\\\\\boxed{r=\sqrt{\dfrac{3V}{\pi h}}}[/tex]
For V=50, h=15, this is ...
[tex]{r=\sqrt{\dfrac{3(50)}{\pi(15)}}=\sqrt{\dfrac{10}{\pi}}\approx\boxed{1.78\quad\text{cm}}[/tex]