Question

In the stream running at 2 km/hr a motor boat goes 14 km upstream and back to the starting point in 77 minutes.
Find the speed of the second
motor boat which speed is 5 km/hr more than half of the first motor boat in still water.
Select one:
Other than the given options
20 km/hr
24 km/hr
22 km/hr
16 km/hr​

Answer 1

Let the speed of the motor boat in still water be x kmph.

Speed downstream = (x+2) kmph

Speed upstream = (x-2) kmph

Therefore,

x−2

10

+

x+2

10

=

60

55

x−2

1

+

x+2

1

=

600

55

=

120

11

11x

2

−240x−44=0

(x−22)(11x+2)=0

x=22

Therefore, speed of motor boat in still water = 22 kmph

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Answer 2

Step-by-step explanation:

the answer is 22 km/hr.

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