It took john 12 hours riding his bike to make the round trip to his uncle's. if he averaged 20 mph out and 30 mph back, how long did he travel each way? (round answer to nearest tenth.)

The volume of a spherical hot air balloon v(r) = 4 3 ? r3 changes as its radius changes. the radius is a function of time given by r(t) = 3t. find the instantaneous rate of change of the volume with respect to t at t = 2.