The Iceland team, while rowing, covered a distance of 20 km downstream in 2 hours and the same distance upstream in 5 hours. Find the speed of the stream.

Let's assume the speed in still water and the speed of the stream are 'B' and 'C' respectively.

The Iceland team, while rowing, covered a distance of 20 km downstream in 2 hours and the same distance upstream in 5 hours.

So $$speed\times time = distance$$

2(B+C) = 20    Eq.(i)

5(B-C) = 20    Eq.(ii)
So  Eq.(i) =  Eq.(ii)

2(B+C) = 5(B-C)

2B+2C = 5B-5C

2C+5C = 5B-2B

3B = 7C

$$\frac{B}{C}\ =\ \frac{7}{3}$$

So let's assume B = 7y and C = 3y.

Put the values of 'B' and 'C' in Eq.(i).

2(7y+3y) = 20

(7y+3y) = 10

10y = 10

y = 1

speed of the stream = 3y

= $$3\times1$$

= 3 km/h