# Aptitude - Boats and Streams - Discussion

Discussion Forum : Boats and Streams - General Questions (Q.No. 5)
5.
In one hour, a boat goes 11 km/hr along the stream and 5 km/hr against the stream. The speed of the boat in still water (in km/hr) is:
3 km/hr
5 km/hr
8 km/hr
9 km/hr
Explanation:

 Speed in still water = 1 (11 + 5) kmph = 8 kmph. 2

Video Explanation: https://youtu.be/KQX_mA3tcVA

Discussion:
38 comments Page 1 of 4.

Vinau said:   6 years ago
X+Y=11,
X-Y=5,
X+Y+X-Y=11 + 5,
2X=16.

Then, X=8.
(22)

HARI said:   6 years ago
For finding the speed of the boat in still water = (upstream-downstream/2).
For finding water speed = (upstream+downstream/2).
(6)

Dhanmoni said:   2 years ago
In one hour, the boat goes the downstream = 11 km/h
On the other hand, the boat goes the upstream = 5 km/h,
So, the speed of the b.in still water is = d+uÃ· 2.
= 11+5Ã·2
= 8 km/ h => answer.
(2)

Musoyiti said:   4 years ago
My way of solving is that;

Let the speed of the current be x.

So the speed in still water will be 11-x and 5 +x. Now as these both expressions are same so we use linear equation and find the value of x to be 3. So the speed of the current is 3 km/hr. So the speed of the boat in still water is 11-3=8.

Hence it is 8 km/hr.
(2)

Darkele said:   6 years ago
Note, there is no use of the 1 hour given because the upstream and downstream is sufficient to get the speed of the boat in still water.
(2)

Shandeepsamy said:   6 years ago
Where this 1/2 came from? Please explain.
(2)

Yamini said:   7 years ago
If the speed downstream is a km/hr and speed upstream is b km/hr then,
Speed in still water=1/2(a+b)km/hr.
(1)

Bhavesh said:   7 years ago
What is this same Q is like in 3 hours a boat goes 11 km along the stream and 5 km against the stream the speed of the boat in still water is?
(1)

Subaram said:   10 years ago
Here direction along the stream called downstream and against the stream called upstream. In this question they gave along the stream 11 kmhr against the stream 5 kmhr. So speed still in water = 1/2 (a+b) , here a downstream be up stream as for formula.
(1)

Rz reddy said:   7 years ago
Downstream(D).
Upstream so(U).
D+U = 11.
D-U = 5.
2D = 16.
D = 16/2.
D = 8km/hr.
(1)