Question

a man can row 7.5 kmph in still water. if in a river running at 1.5 km an hour it takes him 50 minutes to row to a place and back how far off is the place?

Answer 1

speed = 7.5+1.5 = 9 kmph

time = 50/60 hours = 5/6 hours

distance = speed x time

= 9 * 5/6

= 15/2

= 7.5 kms

Answer 2

Answer:

3 km far off is the place.

Step-by-step explanation:

Speed of a man in still water is 7.5 km/hr

And speed of that man in running river water is 1.5 km/hr

It takes total time= 50 minutes = 50/60 hr= 5/6 hr

Let the speed of the man be x km/hr

and the speed of the river be y km/hr

Now,Downstream speed = (x+y) km/hr= (7.5+1.5) =9 km/hr

Upsream speed= (x-y) km/hr = ( 7.5-1.5)=6 km/hr

We know Distance = Speed x time

Ratio of speed = 9:6= 3:2

So,Ratio of time = 2:3 [ speed and time always inverse proportion]

Here (2+3)=5→ 5/6 hr

So,2→1/3 hr

Now time is 1/3 hr and speed 1

Distance = 1x(1/3) = 3 km