3.  A boat goes 30 km upstream and 44 km downstream in 10 hours. In '13 hours it can go 40 km upstream and 55 km downstream. Determine the speed of the stream and that of the boat in still water.

4.  x takes 3 hours more than y to walk 30 km. But if x doubles his pace, he is ahead  of y by one and a half of hours. Find their speeds.

Hi! consider x = A and y= B

Let the speed of A and B be x km/hr and y km/hr respectively.

We know that,

Given, time taken by A = time taken by B + 3 hr

∴ Time taken by A 3 hr = Time taken by B

Solving (1) and (2), we get

Putting the value of y in equation (1), we get

Thus, the speed of A is  and speed of B is 5 km/hr.

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