Question

A person in a motorboat can row 24 km downstream and
30 km upstream in 7 hours. He can also row 36 km
downstream and 24 km upstream in 7 hours. Find the speed
of the motorboat in the stream

Answer 1

A boat goes 24 km upstream and 28 km down stream in 6 hours. It goes 30 km upstream and 21 km downstream in 6 hours and 30 minutes. The speed of the boat in still water is

Let speed of boat in still water be a km/hr.

Let rate of the current be b km/hr.

∴ Speed of the boat upstream =(a−b) km/hr.

∴

a−b

24

+

a+b

28

=6 ...(i)

and

a−b

30

+

a+b

21

=

2

13

..(ii)

From (i) and (ii), we have

a−b

1

=

6

1

and

a+b

1

=

14

1

⇒a−b=6 and a+b=14

⇒a=10 km/hr.