Question
A boat takes 270 minutes to travel 90 km in upstream.
The same boat in the same stream takes 120 minutes to travel 50 km in downstream. Find the distance travelled by the boat while travelling in still water for 360 minutes.Solution
Distance travelled by the boat while travelling in upstream for 1 hour = 90 × (60/270) = 20 km Distance travelled by the boat while travelling in downstream for 1 hour = 50 × (60/120) = 25 km So, upstream and downstream speed of the boat are 20 km/h and 25 km/h, respectively So, speed of the boat in still water = (20 + 25) ÷ 2 = 22.5 km/h So, distance travelled by the boat travelling in still water for 360 minutes = 22.5 × (360/60) = 135 km
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