A van travels for 3 hours at an average speed of 40 mph. How much longer must the van travel at an average of 55 mph so that the average speed for the entire trip will be 50 mph?

Answer 1

6 hours

Answer 2

Can you explain how you got that please?

Answer 3

d1 = V1*T1 = 40 * 3 = 120 mi.

d2 = V2*T2 = 55 * T2 = 55T2.

Vavg. = (d1+d2)/(T1+T2) = 50 mi/h.
(120+55T2)/(3+T2) = 50.
120 + 55T2 = 150 + 50T2.
5T2 = 30.
T2 = 6 Hours.