Ratio of the difference between the downstream and upstream speed of the boat to the upstream speed of the boat is 2:3 and the total time taken by the boat to cover 240 km in downstream and 270 km in upstream is 23 hours. Find the speed of the boat in still water.
a) 28 km/hr
b) 24 km/hr
c) 20 km/hr
d) 16 km/hr
Sol:
Difference between the downstream and
upstream speed of the boat = 2x km/hr
Upstream speed of the boat = 3x km/hr
Speed of the current = 2x/2 = x km/hr
Speed of the boat in still water = 3x + x = 4x
km/hr
240/(4x + x) + 270/3x = 23
48/x + 90/x = 23
138/x = 23
x = 6 km/hr
Speed of the boat in still water = 4 * 6 = 24 km/hr
