Question

A spherical helium balloon has a diameter of 30 cm. How much helium is needed to fill the balloon, in cubic centimeters? Round your answer to the nearest centimeter

Answer 1

from V= 4/3*pi*r^3
dV/dt = 4pi(r^2)dr/dt
so when dV/dt=30 and r = 19
30 = 4pi(361)dr/dt
dr/dt = 30/[4pi(361)]

now in
A = 4pir^2
dA/dt = 8pi(r)dr/dt
= 8pi(19)*30/[4pi(361)]
= you finish it.
HOPE THIS HELPS.