Question 41

A boat takes a total time of twelve hours to travel 105 kms upstream and the same distance downstream. The speed of the boat in still water is six times of the speed of the current. What is the speed of the boat in still water? (in km/hr)

Solution

Let speed of current = $$x$$ km/hr

=> Speed of boat in still water = $$6x$$ km/hr

Acc. to ques, => $$\frac{105}{7x} + \frac{105}{5x} = 12$$

=> $$\frac{15}{x} + \frac{21}{x} = 12$$

=> $$\frac{36}{x} = 12$$

=> $$x = \frac{36}{12} = 3$$

$$\therefore$$ Speed of boat in still water = $$6 \times 3 = 18$$ km/hr

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