26. A motor boat whose speed is 15 km/hr in still water goes 30 km down stream and comes back in a total of 4 hours 30 minutes. determine the speed of the stream
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26. A motor boat whose speed is 15 km/hr in still water goes 30 km down stream and comes back in a total of 4 hours 30 minutes. determine the speed of the stream
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Let the speed of the stream be x km/hr. Then,
Speed downstream = (15 + x) km/hr,
Speed upstream = (15 - x) km/hr.
30 + 30 = 4 1
(15 + x) (15 - x) 2
900 = 9
225 - x2 2
9x2 = 225
x2 = 25
x = 5 km/hr.
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Answer:
Let the speed of the stream be x km/hr. Then,
Speed downstream = (15 + x) km/hr,
Speed upstream = (15 - x) km/hr
So we know from question that it took 4(1/2)hrs to travel back to same point.
So,
\begin{aligned}
\frac{30}{15+x} - \frac{30}{15-x} = 4\frac{1}{2} \\
=> \frac{900}{225 - x^2} = \frac{9}{2} \\
=> 9x^2 = 225 \\
=> x = 5 km/hr