Question

A motorboat takes 6 hrs to cover 100km downstream and 30 km upstream . if the boat goes 75 km downstream and returns back to the starting point in 8 hrs. Find the speed of the boat in still water and speed of the stream

Answer 1

Speed of boat is 20kmph
Speed of water is 5 kmph

Answer 2

Answer:

Let the speed of the stream be x km\hr.

The speed of the boat upstream = (18 - x) km/hr

The speed of the boat downstream = (18 + x) km/hr

Distance = 24 km

As given in the question,

Time for upstream = 1 + Time for downstream

24/(18 - x) = 1 + 24/(18 + x)

24/(18 - x) - 24/(18 + x) = 1

x2 + 48x - 324 = 0

(x + 54)(x - 6) = 0

x ≠ - 54 as speed cannot be negative.

x = 6

The speed of the stream = 6 km/hr

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