Question 74

A boatcovers 64 km upstream in 8 hours and 120 km downstream in 12 hours. Whatis the speed (in m/s)ofthe boat in still water

Solution

downstream speed = $$\frac{distance}{time}$$

downstream speed = $$\frac{120}{12}$$

=10km/hr

upstream speed = $$\frac{distance}{time}$$

upstream speed = $$\frac{64}{8}$$

= 8km/hr

Speed of the boat in still water =$$\frac{speed of upstream + speed of downstream}{2}$$

= $$\frac {10 + 8} {2}$$

= 9km/hr

Change into m/s

=$$(9)\times \frac{5}{18}$$ =2.5 m/s

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