Question

A boat goes 11km an hour in still water but takes four times as much time in going the same distance against the current. The speed of the current is

Answer 1

Hi there!!!

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Let the velocity of the boat be v km/h and velocity of the current be u km/h. 

When the boat goes in still water, its velocity is v=6 km/h. 

When the boat goes against the current, its velocity is v-u=(6-u) km/h. 

For distance S, time taken in still water to cover the distance = S/6 hous 

For same distance S, time taken while going against the current = S/(6-u) hours. 

According to given, S/(6-u) = 3*(S/6) 

=> 1/(6-u) = 1/2 

=> 6-u = 2 

=> u=4 km/h. 

So, the speed of the current is 4 km/h.

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Hope it helps