Question

a man wants to cross a river of width 500m in minimum distance. The rowing a speed of man relative to water is 3 km/h and river flows with speed 2km/h. The time taken by man to cross the river is

Joshi sir comment

for minimum drift he should swim in a direction such that 3sinA = 2

so sinA = 2/3 

now calculate cosA

then time = 500/3cosA

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