Boats, Streams and Trains Quiz: Quantitative Aptitude Practice

Spoilers! These are the Starter quiz’s answers. Easy, Medium, Hard and Mixed rounds show their own answers when you finish.

1. A train 240 m long passes a signal post in 12 seconds. What is its speed?

   • 72 km/h
   • 60 km/h
   • 80 km/h
   • 66 km/h

   Answer: 72 km/h. Passing a post, the train covers only its own length: 240/12 = 20 m/s = 20 × 18/5 = 72 km/h.

2. A train 180 m long running at 54 km/h crosses a platform 270 m long. How long does it take?

   • 25 s
   • 27 s
   • 30 s
   • 36 s

   Answer: 30 s. 54 km/h = 15 m/s. Distance = train + platform = 450 m, so time = 450/15 = 30 s.

3. Two trains 150 m and 200 m long run on parallel tracks in opposite directions at 50 km/h and 76 km/h. How long do they take to cross each other?

   • 12 s
   • 10 s
   • 9 s
   • 14 s

   Answer: 10 s. Opposite directions: relative speed = 126 km/h = 35 m/s. Distance = 350 m, so time = 10 s.

4. A 300 m train running at 90 km/h overtakes a 200 m train running at 54 km/h in the same direction. How long does the overtaking take?

   • 40 s
   • 45 s
   • 55 s
   • 50 s

   Answer: 50 s. Same direction: relative speed = 36 km/h = 10 m/s. It must cover both lengths, 500 m: 500/10 = 50 s.

5. A train 210 m long running at 63 km/h passes a man walking at 9 km/h in the same direction. How long does it take to pass him?

   • 14 s
   • 12 s
   • 10.5 s
   • 15 s

   Answer: 14 s. Relative speed = 63 − 9 = 54 km/h = 15 m/s. The man has no length, so time = 210/15 = 14 s.

6. A boat goes downstream at 16 km/h and upstream at 10 km/h. What is the speed of the stream?

   • 6 km/h
   • 3 km/h
   • 4 km/h
   • 2.5 km/h

   Answer: 3 km/h. Stream speed = (downstream − upstream)/2 = (16 − 10)/2 = 3 km/h. The full difference 6 is the trap.

7. A boat whose speed in still water is 15 km/h goes 36 km downstream and comes back. If the stream flows at 3 km/h, how long does the round trip take?

   • 4.8 hours
   • 5.5 hours
   • 5 hours
   • 6 hours

   Answer: 5 hours. Downstream 18 km/h: 36/18 = 2 h. Upstream 12 km/h: 36/12 = 3 h. Total 5 hours.

8. A man rows 30 km downstream in 2 hours 30 minutes and 18 km upstream in 3 hours. What is his speed in still water?

   • 8 km/h
   • 10 km/h
   • 7.5 km/h
   • 9 km/h

   Answer: 9 km/h. Downstream speed = 30/2.5 = 12 km/h; upstream = 18/3 = 6 km/h. Still-water speed = (12 + 6)/2 = 9 km/h.

9. A man takes twice as long to row a distance upstream as to row the same distance downstream. What is the ratio of his speed in still water to the speed of the stream?

   • 2:1
   • 3:1
   • 3:2
   • 4:1

   Answer: 3:1. Upstream speed is half the downstream speed: u − v = (u + v)/2, so u = 3v. Ratio 3:1.

10. A train crosses a 160 m platform in 18 seconds and a 340 m platform in 27 seconds. What is the length of the train?

    • 180 m
    • 240 m
    • 200 m
    • 220 m

    Answer: 200 m. The extra 180 m of platform takes 9 s more, so speed = 20 m/s. Length = 20 × 18 − 160 = 200 m.