A river is flowing at a speed of 5, km/h in a | vedclass

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(B) Let the speed of the man in still water be $u = 20\, km/h$ and the speed of the river flow be $v = 5\, km/h$.When swimming along the direction of

Vedclass · Accepted Answer

$3\, h\, 12\, min$

Vedclass · Answer

(B) Let the speed of the man in still water be $u = 20\, km/h$ and the speed of the river flow be $v = 5\, km/h$.When swimming along the direction of the flow (downstream),the effective speed is $u + v = 20 + 5 = 25\, km/h$.The time taken to travel from $A$ to $B$ is $t_1 = \frac{Distance}{Speed} = \frac{30}{25} = 1.2\, hours$.When swimming against the direction of the flow (upstream),the effective speed is $u - v = 20 - 5 = 15\, km/h$.The time taken to travel from $B$ back to $A$ is $t_2 = \frac{30}{15} = 2\, hours$.The total time taken is $T = t_1 + t_2 = 1.2 + 2 = 3.2\, hours$.Converting $0.2\, hours$ to minutes: $0.2 	imes 60 = 12\, minutes$.Thus,the total time is $3\, h\, 12\, min$.

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