<PRE><B>Question 902944</B>
A man wishes to cross a river perpendicularly.in still water, he takes 4 min to cross the river, but in flowing river he takes 5 minutes.
if the river is 100 meters wide, then the velocity of the flowing water of the river is:
:
Distance varies directly with time
Find speed of the man in the water
100/4 = 25 meters/min
let v = the velocity of the water in meters/min
:
Use pythag:
100^2 + (5v)^2 = (5*25)^2
10000 + 25v^2 = 15625
25v^2 = 15625 - 10000
25v^2 = 5625
v^2 = 5625/25
v^2 = 225
v = {{{sqrt(225)}}}
v = 15 m/min velocity of the river
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