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Two places were 81 km apart. Two boats start from both places at the same time towards each other. If one boat is going downstream then the other one is going upstream. After how much time will they meet each other if their speeds are 12 km/hour and 15 km/hour in still water respectively?

Two places were 81 km apart. Two boats start from both places at the same time towards each other. If one boat is going downstream then the other one is going upstream. After how much time will they meet each other if their speeds are 12 km/hour and 15 km/hour in still water respectively? Correct Answer 3 hours

GIVEN:

Distance = 81 km

Speed of first boat in still water = 12 km/hour

Speed of Second boat in still water = 15 km/hour

FORMULA USED:

Downstream speed = Speed of boat + Speed of water

Upstream speed = Speed of boat – Speed of water

Relative speed = Speed of First boat + Speed of Second boat

Time = Distance/speed

CALCULATION:

Let the speed of water be ‘W’

Downstream speed = (12 + W)

Upstream speed = (15 – W)

Relative Speed = 12 + W + 15 – W = 27 km/hour

∴ Required time = 81/27 = 3 hours

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