Question

A boat covers 32 Km upstream and 36km downstream in 7 hours. Also, it covers 40 km upstream and 48 km downstream in 9 hours. Find the speed of boat in still water.
plzzz give a good description

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Answer 1

Answer:

let the speed of boat be = x km/hr

and that of stream be = y km/hr

Now, we can say that when the boat moves upward, it moves against the stream, so its effective speed would be = (x-y) km/hr

and when it comes downstream it goes along the stream so its effective speed would be = (x+y) km/hr

we know that time=distance/speed

ATQ,

7=32/x-y + 36/x+y

and 9=40/x-y + 48/x+y

now let 1/x-y be = a and 1/x+y be = b

Here we get two new equations,

32a + 36b = 7 and 40a + 48b = 9

Now solve them and get your answer.

We get a = 1/8 and b = 1/12

=> x-y=8 and x+y=12

=> x = 10 and y = 2.

Hence, the speed of boat is 10 km/hr.