A motorboat travels 40 Km downstream in 4 hours and 30 Km upstream in 5 hours. Find the speed of the stream(in Km/hr).
A motorboat travels 40 Km downstream in 4 hours and 30 Km upstream in 5 hours. Find the speed of the stream(in Km/hr).
The correct option is A 2 Km/hr
Consider, a boat moving at a speed of S1 and the speed of the water stream is S2.
If the stream and boat are moving in the same direction(Downstream or along the stream), the Effective speed of the boat = S1 + S2
And, If the stream and boat are moving in the opposite direction(Upstream or against the stream), the Effective speed of the boat = S1 - S2
The speed of the boat along the stream(downstream) = S1 + S2 = 40 Km/ 4 hrs = 10 Km/hr ---------(1)
The speed of the boat against the stream(upstream) = S1 -S2 = 30 Km/5 hrs = 6 Km/hr ---------------(2)
We have two equations now, and we need the speed of the stream, ie, S2
So, (1) - (2) will give us 2 S2 = 4 Km/hr or S2 = 2 km/hr
2 Km/hr
Consider, a boat moving at a speed of S1 and the speed of the water stream is S2.
If the stream and boat are moving in the same direction(Downstream or along the stream), the Effective speed of the boat = S1 + S2
And, If the stream and boat are moving in the opposite direction(Upstream or against the stream), the Effective speed of the boat = S1 - S2
The speed of the boat along the stream(downstream) = S1 + S2 = 40 Km/ 4 hrs = 10 Km/hr ---------(1)
The speed of the boat against the stream(upstream) = S1 -S2 = 30 Km/5 hrs = 6 Km/hr ---------------(2)
We have two equations now, and we need the speed of the stream, ie, S2
So, (1) - (2) will give us 2 S2 = 4 Km/hr or S2 = 2 km/hr
