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If The speed of a man is  2 \mathrm{~km} / \mathrm{hr}  in still water. man makes his strokes perpendicular to the River flow. having width of 1 \mathrm{~km} man Reaches a point  800 \mathrm{~m} downstream on the opposite. Bank. find the speed of the River water is

Option: 1

\frac{8}{5} \mathrm{~km} / \mathrm{hr} \\


Option: 2

8 \mathrm{~km} / \mathrm{hr} \\


Option: 3

3 \mathrm{~km} / \mathrm{hr} \\


Option: 4

1 \mathrm{~km} / \mathrm{hr} .


Answers (1)

best_answer

Speed =\frac{\text { Distance }}{\text { Time }} \\
t =\frac{1 \mathrm{~km}}{\text { Speed }}=\frac{1 \mathrm{~km}}{v_m} \\

v_m =\frac{1}{t}=\frac{1000}{t}..........(1)

V_R=\frac{800}{t} \\

800=V_R \times t \\


 V_R=\frac{800}{t}-2.............(2)


\frac{V_m}{V_R}=\frac{1000}{800} =\frac{5}{4} \\

V R=\frac{4}{5} V_m =\frac{4}{5} \times 2 \\


=\frac{8}{5} \mathrm{~km} / \mathrm{hr} .


 

Posted by

chirag

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