Question : A watercraft is rowed down 32 km along a river in 4 hours and 10 km against the river in 5 hours. Find the speed of the watercraft and that of the river.
4.5 km/h and 2.5 km/h4 km/h and 3 km/h
5 km/h and 3 km/h
3.5 km/h and 1.5 km/h
Solution:
$\require{cancel}$
স্রোতের অনুকূলে নৌকার গতিবেগ = $ \cfrac{\cancelto{8}{32}}{\cancel{4}} = 8 $ km/h.
স্রোতের প্রতিকূলে নৌকার গতিবেগ = $ \cfrac{\cancelto{2}{10}}{\cancel{5}} = 2 $ km/h.
∴ নৌকার গতিবেগ = $ \cfrac{8+2}{2} =\cfrac{\cancelto{5}{10}}{\cancel{2}} = 5 $ km/h.
এবং নদীর স্রোতের বেগ = $ \cfrac{8-2}{2} = \cfrac{\cancelto{3}{6}}{\cancel{2}} = 3 $ km/h.
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