A stream flows at 3 km/h. A boat can row 9 km/h in still water. How much time does it take to go 24 km downstream and return upstream to the starting point?
A car driver leaves Bangalore at 8:30 AM and expects to reach a place 300 km away at 12:30 PM. At 10:30 AM he finds that he has covered only 40% of the distance. By how much must he increase the speed of the car to reach on scheduled time?
Explanation:
Total time available = 4 hours. At 10:30 AM (after 2 hours), distance covered = 40% of 300 = 120 km. Remaining distance = 180 km. Remaining time = 12:30 PM - 10:30 AM = 2 hours. Required speed = 180 / 2 = 90 km/h. Original speed = 120 / 2 = 60 km/h. Increase in speed = 90 - 60 = 30 km/h.
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