# 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:

Answer: Option

Explanation:

Discussion:

38 comments Page 1 of 4.
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.

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.

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)

A.K.BALAKRISHNAN said:
5 years ago

@All.

Follow this method for all boat question;

Downstream means boat towards the down in this situation we have to find the speed of boat and speed of stream.

Let x be boat speed.

Let y be stream speed.

1) Down stream speed = D/T(downstream time) = x+y

note: distance will be the same as both the streams.

2) Upper stream speed = D/T (upper stream time) = x-y.

Thank you.

Follow this method for all boat question;

Downstream means boat towards the down in this situation we have to find the speed of boat and speed of stream.

Let x be boat speed.

Let y be stream speed.

1) Down stream speed = D/T(downstream time) = x+y

note: distance will be the same as both the streams.

2) Upper stream speed = D/T (upper stream time) = x-y.

Thank you.

Vinau said:
6 years ago

X+Y=11,

X-Y=5,

X+Y+X-Y=11 + 5,

2X=16.

Then, X=8.

X-Y=5,

X+Y+X-Y=11 + 5,

2X=16.

Then, X=8.

(22)

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.

(1)

Shandeepsamy said:
6 years ago

Where this 1/2 came from? Please explain.

(2)

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).

For finding water speed = (upstream+downstream/2).

(5)

Nurun Nobi Khokon said:
6 years ago

Let, downstream (with stream) speed= x.

upstream (against) speed is= y.

Now,

x = speed of the boat+speed of the water.

y = speed of the boat-speed of water.

-----------------------------------------------------------

x+y = 2*speed of the boat.

So, speed of the boat = (x+y)/2 [downstream speed+upstream speed].

upstream (against) speed is= y.

Now,

x = speed of the boat+speed of the water.

y = speed of the boat-speed of water.

-----------------------------------------------------------

x+y = 2*speed of the boat.

So, speed of the boat = (x+y)/2 [downstream speed+upstream speed].

(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.

Upstream so(U).

D+U = 11.

D-U = 5.

2D = 16.

D = 16/2.

D = 8km/hr.

(1)

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.

Speed in still water=1/2(a+b)km/hr.

(1)

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