The cylindrical water tank on a semitrailer has a length of 20 feet. The volume of the tank is equal to the product of pi, the s
quare of the radius of the tank, and the length of the tank. Let V represent the volume of the tank, r represent the radius of the tank, h represent the length of the tank. Create an equation could be used to find volume, V, of the cylindrical tank.
Calvin's first leg of the trip took 0.5 hr (30 minutes) at 6 mph. That means he travelled (0.5hr x 6 mph =) 3 miles. He travelled 3 miles on the return trip, by definition (same path home). At 18 mph, 3 miles would take (3 miles/18 mph =) 0.1667 hours. That makes a total of 6 miles and (0.5 + 0.1667=) 0.6667 hours.
(6 miles)/(0.6667 hours) = 9 mph is Calvin's average speed for the round trip.