# Aptitude - Boats and Streams - Discussion

Discussion Forum : Boats and Streams - General Questions (Q.No. 14)

14.

A man takes twice as long to row a distance against the stream as to row the same distance in favour of the stream. The ratio of the speed of the boat (in still water) and the stream is:

Answer: Option

Explanation:

Let man's rate upstream be *x* kmph.

Then, his rate downstream = 2*x* kmph.

(Speed in still water) : (Speed of stream) = | 2x + x |
: | 2x - x |
||||

2 | 2 |

= | 3x |
: | x |

2 | 2 |

= 3 : 1.

Discussion:

30 comments Page 1 of 3.
Jamshaid said:
2 years ago

Here, the shortest way is

2(A-B) = A+B.

A/B = 3/1.

2(A-B) = A+B.

A/B = 3/1.

(3)

Aruna said:
3 years ago

There is a formula.

B/S = (T1 + T2) / (T1 ~ T2).

Here,

* B is the speed of boat in still water.

* S is the speed of stream/current/river.

* T1 is the time taken in upstream/ downstream.

* T2 is the time taken in downstream/ upstream.

Given:

Twice as long to row ' against' the stream (is. Upstream) as to row same distance in 'favor' of the stream(ie. downstream).

Solution:

Upstream : downstream

Time: 2 : 1 ( T1 = 2 *T2 )

So, T1 = 2 and T2 = 1.

Apply in the formula,

B/S = (2+1)/(2-1) = 3/1.

B:S = 3:1.

B/S = (T1 + T2) / (T1 ~ T2).

Here,

* B is the speed of boat in still water.

* S is the speed of stream/current/river.

* T1 is the time taken in upstream/ downstream.

* T2 is the time taken in downstream/ upstream.

Given:

Twice as long to row ' against' the stream (is. Upstream) as to row same distance in 'favor' of the stream(ie. downstream).

Solution:

Upstream : downstream

Time: 2 : 1 ( T1 = 2 *T2 )

So, T1 = 2 and T2 = 1.

Apply in the formula,

B/S = (2+1)/(2-1) = 3/1.

B:S = 3:1.

Mani said:
3 years ago

Hi, but in this question upstream is same as downstream then for both it would be twice then how you could say upstream is x downstream is 2x?

(1)

Fathima Sulfikkar said:
4 years ago

Distance is same.

D (up)=D (down); also t (u)= 2t (d)

Speed of boat=b: speed of current = s.

D (u) = D (d).

t (u)(b-s) = t (v)(b+s).

2t (v)(b-s) = t (v)(b+s).

2b-2s = b+s.

2b-b = s+2s.

b = 3s.

b/s = 3/1.

D (up)=D (down); also t (u)= 2t (d)

Speed of boat=b: speed of current = s.

D (u) = D (d).

t (u)(b-s) = t (v)(b+s).

2t (v)(b-s) = t (v)(b+s).

2b-2s = b+s.

2b-b = s+2s.

b = 3s.

b/s = 3/1.

(2)

Swetha reddy said:
4 years ago

How the speed of the boat in still water is (2x+x) /2?

Ragi k r said:
5 years ago

The speed of boat= B, speed of river= R.

upstream=x=B-R -----> (1)

downstream=2x=B+R -----> (2)

So, (1)+(2).

2B=3x

B=x(3/2)

B+R=2x.

=>R=2x-B =>R=2x-(3/2)x =>R=x/2.

B:R=3/2 : 1/2 = 3:1.

upstream=x=B-R -----> (1)

downstream=2x=B+R -----> (2)

So, (1)+(2).

2B=3x

B=x(3/2)

B+R=2x.

=>R=2x-B =>R=2x-(3/2)x =>R=x/2.

B:R=3/2 : 1/2 = 3:1.

Shalinee said:
6 years ago

Here we use this formula and simply find the ratio.

Sb/Ss =n+1/n-1 then,

Sb/Ss = 2+1/2-1,

Sb/Ss =3/1 so.

Then we will get,

Sb:Ss = 3:1.

Sb/Ss =n+1/n-1 then,

Sb/Ss = 2+1/2-1,

Sb/Ss =3/1 so.

Then we will get,

Sb:Ss = 3:1.

(1)

Manoj said:
6 years ago

The distance is same so,

D/t = x.

where x is the speed of the boat in downstream.

D/t = 2x in upstream case.

D/t = x.

where x is the speed of the boat in downstream.

D/t = 2x in upstream case.

Sajith said:
6 years ago

Let d= distance and x = time.

Speed in still water = 1/2(speed in down stream + speed in up stream).

= 1/2 (d/x + d/2x) => eqn 1.

Rate of stream = 1/2( speed in down stream - speed in up stream).

= 1/2(d/x - d/2x) => eqn 2;

We need eqn 1 : eqn 2.

On simplification, we will get 3:1.

Speed in still water = 1/2(speed in down stream + speed in up stream).

= 1/2 (d/x + d/2x) => eqn 1.

Rate of stream = 1/2( speed in down stream - speed in up stream).

= 1/2(d/x - d/2x) => eqn 2;

We need eqn 1 : eqn 2.

On simplification, we will get 3:1.

Vishi said:
6 years ago

Boat speed(B) +stream speed (S).

B+S = x

B-S = 2x

BY adding

2B = 3x

B= 1.5 x

By substracting

2S = -x

S= -.5 on neglecting - sign .5x

Ration becomes .5 : 1.5

Which is 1:3 also

Stream speed : boat speed.

B+S = x

B-S = 2x

BY adding

2B = 3x

B= 1.5 x

By substracting

2S = -x

S= -.5 on neglecting - sign .5x

Ration becomes .5 : 1.5

Which is 1:3 also

Stream speed : boat speed.

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