| Question | A motorboat travels 16 km in 2 hours against the flow of river and travels next 8 km along the flow of the river in 20 minutes. How long will it take motorboat to travel 48 km in still water? | |
| Type | multiple_choice | |
| Option | 2.5 hours | incorrect |
| Option | 3 hours | correct |
| Option | 3.5 hours | incorrect |
| Option | 4 hours | incorrect |
Speed = Distance / Time
Speed upstream = 19/2 = 8 km/hr
Speed downstream = 8/20/60 = 480/20 = 24 km/hr
∴ Speed in still water = = 1/2 (speed downstream +speed upstream)
= 1/2 ( 24 + 8) = 16 km/hr
Required time = Distance/ Speed still water
= 48/16 = 3 hour
