Question 43

A boat travels upstream from B to A and downstream from A to B in 3 h. If the speed of the boat in still water is 9 km/h and the speed of the current is 3 km/h, what is the distance between A and B?

Solution

Speed of the boat upstream =9-3 =6 km/hr

Speed of the boat downstream=9+3=12 km/hr

Let the distance between A and B be x kms.

So,time taken to travel x km upstream by boat= x/6 hrs.

And time taken to travel x kms downstream = x/12 hrs.

According to the question ,

x/6 + x/12 =3

x[1/6 + 1/12]=3

x = 4×3 =12

So, distance between A and B is 12 kms.

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