David is visiting his aunt for the Thanksgiving weekend. He drove 60% of the trip at 40 mph and the rest at ‘x’ mph. The average speed for the entire trip is 50 mph. What is x? A. 60 mph B. 70 mph C. 75 mph D. 80 mph E. 90 mph F. 100 mph

D. 80 mph

Step-by-step explanation:

d- distance

constant acceleration- a

constant velocity- c

no velocity or acceleration- b

explanation:

for body moving with a constant acceleration, the rate of change of displacement changes over time. this is proven by the increasing gradient of the curve (a) against time.

a body that is moving at constant velocity covers equal distances over equal periods of time, thus the straight line with a constant gradient c.

a stationary body   covers no displacement as time elapses. thus the flat line with   zero gradient.