Question

j

Answer 1

ok... is the surface area is 20 the

\[20 = 4\pi r^2\]

find the value of r

you know

\[V = \frac{4}{3} \pi r^3\]

you need to find

\[\frac{dV}{dr}\]

and you know

\[\frac{dV}{dt} = 10\]

you need to use the chain rule to find \[\frac{dr}{dt}\]

so

\[\frac{dV}{dt} = \frac{dV}{dr} \times \frac{dr}{dt}\]

or

\[10 = 4 \pi r^2 \times \frac{dr}{dt}\]

just substitute the r value found from the surface area and solve for dr/dt