S = (90 + 42)/2 = 66 kmph
This justifies what answer for what question? Q & A:
The speed of a car is 90 km in the first hour and 42 km in the second hour. What is the average speed of the car?
Options:
(A) 89 kmph
(B) 92 kmph
(C) 75 kmph
(D) 65 kmph
(E) 66 kmph
(E)