Distance between a point of A and point B in a river is 12 km and the flow of the stream is from A to B. If the speed of the boat is 4 km/h and speed of the stream is 2 km/h. The boat goes from B to A and then comes back. What is the distance between point A and the boat after 7 hours of travel since the time of starting?
2 km
3 km
4 km
6 km
Explanation:
The resulting speed in upstream is 4 – 2= 2 km/h.
And the resulting speed in downstream is 4 + 2= 6 km/h.
Since the boat is moving upstream from B to A.
So time taken is 12/2 =6 hours.
Now in downstream it takes 12/6 =2 hours
So in 1 hour it will travel half the distance = 6 km.
So the distance of the boat from point A after 7 hours of travel will be 6 km.
The resulting speed in upstream is 4 – 2= 2 km/h.
And the resulting speed in downstream is 4 + 2= 6 km/h.
Since the boat is moving upstream from B to A.
So time taken is 12/2 =6 hours.
Now in downstream it takes 12/6 =2 hours
So in 1 hour it will travel half the distance = 6 km.
So the distance of the boat from point A after 7 hours of travel will be 6 km.