Question

A motorboat, whose speed in 15 km/hr in still water goes 30 km downstream and comes back in a total of 4 hours 30 minutes. The speed of the stream (in km/hr) is

Answer 1

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Answer 2

Answer:

Answer: speed = 5km/hr.

Explanation:

Let speed of the stream = x.

Speed of downstream = (15 +x) km/hr.

Speed of upstream = (15-x) km/hr.

time = distance/speed.      -(1)

time = 4hr 30min = 4 1/2 hr = 9/2 hr.

distance = 30km.

Therefore, using (1), we get,

30/15+x + 30/15-x = 9/2

900/(225-x^2) = 9/2

900*2/9 = 225-x^2

200 = 225 -x^2

x^2 = 25

x = $\sqrt{25$ = 5.

Therefore, speed of the stream = 5 km/hr.

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