Question

A man rows 12km in 5h against the stream, the speed of current being 4km/h. What time will be taken by him to row 15km with the stream?

Answer 1

$\bf\red{Answer}$

Speed of current 'y' = 4km/h

Distance = 12 km.

Speed in upstream = x−y km/hr.

Here 'x' is speed of boat in still water

$\sf Speed = \frac{Distance}{time}$

$\sf x−4=125$

$\sf 5x−20=12$

$\sf 5x=32$

$\bf x=6.4 km/hr$

speed in dowstream =(x+y)

$\sf =6.4+4=10.4 km / h$

∴Time=DistanceSpeed

$\sf Time= \frac{15}{10.4} = \frac{150}{104}$

$\sf = 1 hour \: 26 \: \frac{7}{13}minutes$

Answer 2

Answer:

1 hour 16 minutes

Step-by-step explanation:

We find the seed of man in up stream

speed of man in up stream=2.4km per hour.

Now

we find speed of man in down stream=2*speed of stream+ up stream

=(2*4) +2.4

=8+2.4

=10.4 km per hour

10.4 km is covered in 1 hour

1 km is covered in 1/10.4 hour

15 km is covered in (1/10.4)*15

=150/104=

approximately 1 hour 16 minutes .