CMA Foundation · Fundamentals of Business Mathematics and Statistics · Time and Distance
A motorboat moves at 15 km/h downstream and 9 km/h upstream. What is the speed of the boat in still water and the speed of the stream?
The boat speed in still water is the average of the downstream and upstream speeds, which is 12 km/h, and the stream speed is half their difference, which is 3 km/h. So the correct pair is 12 km/h and 3 km/h.
- A12 km/h and 3 km/hCorrect
- B12 km/h and 6 km/h
- C24 km/h and 3 km/h
- D6 km/h and 3 km/h
Explanation
Still water speed = (15 + 9)/2 = 12 km/h. Stream speed = (15 - 9)/2 = 3 km/h. The option with 6 km/h wrongly uses the full difference 15 - 9 as the stream speed without halving it.
Did you get it right without looking?
One question tells you little. A timed set on Time and Distance shows your real accuracy, how long you take and where you lose marks.
More Time and Distance questions
- A goods train 300 m long crosses a platform 200 m long in 25 seconds. How long will it take to cross a pole beside the track at the same spe…
- A delivery van from Pune covers 150 km at a uniform speed of 50 km/h. How many minutes does the journey take?
- Ramesh drives from Delhi to Jaipur at 60 km/h and returns along the same route at 40 km/h. What is his average speed for the whole round tri…
- Two trains, 150 m and 100 m long, run on parallel tracks in opposite directions at 54 km/h and 36 km/h respectively. How many seconds do the…
- Three runners start together from the same point of a circular track and run in the same direction at 4 m/s, 6 m/s and 10 m/s. The track is …
- A train 150 m long runs at a speed of 54 km/h. How much time will it take to cross a telegraph pole standing beside the track?