The speed of a boat in still water in 20 km/hr and the rate of current is 4 km/hr. The distance travelled downstream in 24 minutes is:	Choose the correct choice from the following:
A) 9.2
B) 10.2
C) 9.8
D) 9.6
E) 10.0

Rationale: "speed downstream = ( 20 + 4 ) = 24 kmph time = 24 minutes = 24 / 60 hour = 2 / 5 hour distance travelled = time × speed = 2 / 5 × 24 = 9.6 km answer is d ."
Answer: D