Question

A man rows at 5 km/h in still water. If the river is running at 1 km/h, it takes him 75 minutes to row to a place and back. How for is the place?
A) 2.5 km
B) 3 km
C) 4 km
D) 5 km

Answer 1

Speed of boat in still water, s1 = 5 kmph

Speed of river, s2 = 1 kmph

Speed in upstream, (s1-s2) = 4 kmph

Speed in downstream, (s1+s2) = 6 kmph

Now, you can apply either 'proportion technique' or 'tsd' formula

Applying time, speed, and distance formula,

(d/6)+(d/4) = 75/60

Solving, d = 3km