Question

Boat A travels downstream from Point X to Point
Y in 3 hours less than the time taken by Boat B to
travel upstream from Point Y to Point Z. The distance
between X and Y is 20 km, which is half of the
distance between Y and Z. The speed of Boat B in
still water is 10 km/h and the speed of Boat A in
still water is equal to the speed of Boat B upstream.
What is the speed of Boat A in still water? (Consider
the speed of the current to be the same.)​

Answer 1

Answer:

8  km/hr

Step-by-step explanation:

The distance  between X and Y is 20 km

the  distance between Y and Z = 2 * 20 = 40 km

The speed of Boat B in  still water is 10 km/h

Let say Speed of Stream = S km/Hr

Speed of Boat B upstream = 10 - S km/hr

Speed of Boat A in still water = 10 - S km/hr

Speed of Boat A Downstream = 10-S + S = 10 km/hr

Boat B to  travel upstream from Point Y to Point Z

Time taken = 40/(10 -S) hr

Boat A travels downstream from Point X to Point  Y

Time Taken = 20/10 = 2 hr

2 = 40/(10 -S) - 3

=> 5 = 40/(10 -S)

=> 1 = 8/(10 -S)

=> 10-S = 8

=> S = 2

Speed of Boat A in still water = 10 - 2 = 8  km/hr