Question 31

A boat moves downstream at the rate of 1 km in $$ 7\frac{1}{2} $$ minutes and upstream at the rate of 5 km an hour, What is the speed (in km/hour) of the boat in the still water?

Solution

Downstream speed = $$\frac{1}{\frac{15}{2 \times 60}} = 8 km/hr$$

Upstream speed = 5 km/hr

Speed of boat in still water = $$\frac{8 + 5}{2}$$ = 6.5 km/hr

So, the answer would be option d)$$ 6\frac{1}{2} $$

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