The speed of a car is 90 km in the first hour and 80 km in the second hour. What is the average speed of the car?
Choose the correct option.
A) 12  B) 75  C) 85  D) 54  E) 15

Rationale: "s = ( 90 + 80 ) / 2 = 85 kmph answer : c"
Answer: C