The speed of a boat in still water is 15 km/hr and the rate of current is 3 km/hourr. The distance travelled downstream in 24 mins is?	Choose one.
A) 6 km	B) 7 km	C) 7.2 km	D) 8 km	E) 8.4 km

Rationale: "speed of a boat in still water = 15 km / hr speed of the current = 3 km / hr speed downstream = ( 15 + 3 ) = 18 km / hr distance travelled downstream in 24 minutes = 2460 × 18 = 2 × 185 = 7.2 km c"
Answer: C