Question

A Boat takes 9 hours to travel a distance upstream and takes 3 hours to travel the same distance downstream give the speed of boat in still water in 4 km/h. What is the speed of stream?​

Answer 1

Step-by-step explanation:

Continuous......

The velocity of the stream is 8 km/hr. The distance covered, d = 36 km.

Check: While going downstream time taken = 36/(4+8) = 3 hours. Correct.

While going upstream time taken = 36/(8–4) = 9 hours.

Answer 2

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Answer:

Let the distance covered by the boat each way be d km. And let the velocity of the stream be v km/hr.

While going downstream the velocity of the boat is (v+4) km/hr.

While going upstream the velocity of the boat is (v-4) km/hr.

d/(v+4) = 3, or

d = 3v +12 …(1)

d/(v-4) = 9, or

d = 9v - 36 …(2).

Equating (1) and (2)

d = 3v +12 = 9v - 36, or

9v-3v = 6v = 12+36 = 48, or

v = 48/6 = 8 km/hr

The velocity of the stream is 8 km/hr. The distance covered, d = 36 km.

While going downstream time taken = 36/(4+8) = 3 hours

While going upstream time taken = 36/(8–4) = 9 hours

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