Solving Related Rates Problems Practice Test

Sand forms a cone whose radius equals half its height; volume increases at $8 , \text{ft}^3/\text{min}$. Find $\frac{dh}{dt}$ when $h=6$ ft.

A point moves on $x^2+y^2=25$ with $\dfrac{dx}{dt}=4$. When $x=3$ and $y=4$, what is $\dfrac{dy}{dt}$?