The average speed of a car decreased by 3 miles per hour every successive 8-minutes interval. If the car traveled 3.6 miles in the fifth 8-minute interval, what was the average speed of the car, in miles per hour, in the first 8 minute interval?  Choose the correct choice from the following answers:
A) 31 B) 35 C) 39 D) 43 E) 47

Rationale: ( 3.6 miles / 8 minutes ) * 60 minutes / hour = 27 mph let x be the original speed . x - 4 ( 3 ) = 27 x = 39 mph the answer is c .
Answer: C