A boat goes 20 km upstream and 30 km downstream in 5 hours each time. What is the speed of that of boat in still water and the speed of the current ?
Answer & explanation
Correct answer: option 3
The correct answer is option (3) : speed of boat in still water is 5 km/h and speed of current is 1 km/h
Let the speed of boat in still water be x km/h and speed of current be y km/hr.
Downstream speed $= x+ y = \frac{30}{5}= 6\, km/hr$
Upstream speed $= x- y = \frac{20}{5}= 4\, km/hr $
Solving both eq simultaneously
we get $x=5, y= 1$
So, speed of boat in still water is 5 km/h and speed of current is 1 km/h