The ratio of speed of a motor-boat to that of the current of water is 17 : 5.…
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The ratio of speed of a motor-boat to that of the current of water is 17 : 5. The boat goes along with the current in 4 hours. It will come back in
- A.
7 hr 20 min
- B.
8 hr 10 min
- C.
7 hr 50 min
- D.
8 hr 20 min
Attempted by 20 students.
Show answer & explanation
Correct answer: A
Solution: Since the ratio 17 : 5 is given.
Let the speed of boat in still water = 17 km/hr and speed of stream = 5 km/hr
Downstream speed = 17 + 5 = 22 km/hr
Upstream speed = 17 – 5 = 12 km/hr
Distance = Downstream speed x downstream time
= 22 x 4 = 88 km
Upstream time = Distance/upstream speed
= 88/12
Come back time = 7 hour 20 minute