# Aptitude - Boats and Streams - Discussion

Discussion Forum : Boats and Streams - Data Sufficiency 2 (Q.No. 1)

*Directions to Solve*

Each of the questions given below consists of a question followed by three statements. You have to study the question and the statements and decide which of the statement(s) is/are necessary to answer the question.

1.

What is the speed of the boat in still water? | |

I. | The speed downstream is 12 kmph. |

II. | The speed upstream is 4 kmph. |

III. | In a to and fro journey between two points, the average speed of the boat was 6 kmph. |

Answer: Option

Explanation:

From I and II, speed of boat in still water = | 1 | (12 + 4) km/hr = 8 km/hr. |

2 |

From II and III, we get:

Using average speed = | 2xy |
, we get: | 2 x 4 x y |
= 6 |

x + y |
4 + y |

8*y* = 24 + 6*y*

*y* = 12.

Required speed = | 1 | (12 + 4) km/hr = 8 km/hr. |

2 |

Similarly, I and III also give the answer.

Correct answer is (D).

Discussion:

11 comments Page 1 of 2.
Kapadiya sagar said:
4 years ago

Options 1 and 3 become same.

a+b = 6kmph.

So with one equation two unknown is not solvable.

So, the Correct option is [A].

a+b = 6kmph.

So with one equation two unknown is not solvable.

So, the Correct option is [A].

ABHILASHA said:
6 years ago

3rd statement itself is enough as [(u+v)+(u-v)]/2=6.

Which gives u = 6; where u is the speed of the boat in still water and v is the speed of the stream.

Which gives u = 6; where u is the speed of the boat in still water and v is the speed of the stream.

Priya said:
6 years ago

123+45=168,

168*0=0,

Therefore the answer is 0.

But unfortunately, the answer is not 0.

Because any answer cannot be 0.

So, we increment the answer by 1 to avoid any problems.

Therefore the answer is 1.

168*0=0,

Therefore the answer is 0.

But unfortunately, the answer is not 0.

Because any answer cannot be 0.

So, we increment the answer by 1 to avoid any problems.

Therefore the answer is 1.

HarshaVardan said:
8 years ago

My Analysis.

Upstream is 4kmps and downstream is 12kmps.

Boat speed still in water =(down stream+upstream)/2 = (1/2) * (12+4) = 8kmps.

Boat speed against the water =(down stream-upstream)/2 = (1/2) * (12-4) = 4kmps.

So, Statments 1&2 are efficient to get this answer.

Answer is Option "A".

Upstream is 4kmps and downstream is 12kmps.

Boat speed still in water =(down stream+upstream)/2 = (1/2) * (12+4) = 8kmps.

Boat speed against the water =(down stream-upstream)/2 = (1/2) * (12-4) = 4kmps.

So, Statments 1&2 are efficient to get this answer.

Answer is Option "A".

Shashi said:
8 years ago

How is statement 3 related to question?

There is no need of 3rd statement or no relation b/w 3rd to another statement.

There is no need of 3rd statement or no relation b/w 3rd to another statement.

Swarnashree said:
9 years ago

Why x is taken as speed of the boat upstream?

Rahul said:
9 years ago

x is the speed of the boat upstream, and y is the speed of the boat downstream.

AASHIT said:
1 decade ago

Why has 4 been substituted for 'x' when 4=x+y?

Aman said:
1 decade ago

Can anybody tell me how we get the value 4 in that average speed formula you have putted.

Amit said:
1 decade ago

Avg. speed = Total distance / Total time = 2L / t1 + t2.

Time = distance / speed so, t1 = L / x and t2 = L / y.

t1 + t2 = L(x+y) / xy.

Total time = L(x+y) / xy.

Total distance = 2L.

Avg. speed = 2xy/x+y.

Time = distance / speed so, t1 = L / x and t2 = L / y.

t1 + t2 = L(x+y) / xy.

Total time = L(x+y) / xy.

Total distance = 2L.

Avg. speed = 2xy/x+y.

(1)

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