The boat covers 108 km upstream and 264 km downstream in 20 hours. The speed of the boat in still water is 75% of the speed of the boat along with the stream. If the speed of the boat is decreased by 33(1/3)% and the speed of stream is increased by 33(1/3)%, then find the time taken by the boat covers 196 km downstream.
A. 9.5 hours
B. 9.8 hours
C. 10.2 hours
D. 10.4 hours
E. 9.2 hours
Sol:
Speed of downstream = 4x
Speed of boat = 75/100 * 4x = 3x
Speed of stream = 4x – 3x = x
108/(3x – x) + 264/4x = 20
120 = 20x
x = 6
Speed of boat after decreased 33(1/3)% = 3 * 6 *
200/300 = 12 kmph
Speed of stream after increased 33(1/3)% =
400/300 * 6 = 8 kmph
Required Time = 196/(12 + 8) = 9.8 hours