A boat travels in upstream. If the speed of boat in upstream is decreased by 40% then it is equal to the speed of current and speed of boat in still water is given as 240 km/hr. Then find upstream speed of boat? (km/hr).

Speed in still water = 240 km/hr. Let boat speed = b, current speed = c. Upstream speed = b - c. When upstream speed decreases by 40%, it equals current speed: 0.6(b - c) = c. Also, b = 240. From 0.6(b - c) = c: 0.6b - 0.6c = c, 0.6b = 1.6c, c = 0.6b/1.6 = 0.375b = 0.375 × 240 = 90 km/hr. Upstream speed = b - c = 240 - 90 = 150 km/hr. Option B is correct.