**Boats and Streams Questions and Answers** – **Formulas & Tricks**

**Upstream**= (X-Y)km/hr, Where “X” is the speed of the boat in still water and “Y” is the speed of the stream**Downstream**= (X+Y)km/hr, Where “X” is the speed of the boat in still water and “Y” is the speed of the stream**Speed of Boat Still Water**= (1/2)(Downstream Speed + Upstream Speed)**Speed of Stream**=(1/2)(Downstream Speed – Upstream Speed)**Average Speed of Boat**= {(Upstream Speed * Downstream Speed) / Boat Speed still water}- If a boat travels a distance downstream n “t1” hrs and returns the same distance upstream in “t2” hrs, then the
**speed of the man in still water**will be = [Y *{(t2+t1)/(t2-t1)}]km/hr, where “Y” is the speed of the stream. - If it takes “t” hrs for a boat to reach a point in still water and comes back to the same point then, the distance between the two points can be calculated by
**Distance ={(u**, where “u” is the speed of the boat in still water and “v” is the speed of the stream.^{2}-v^{2}) * t} /2u - If it takes “t” hrs more to go to a point upstream than downstream for the same distance, the formula for distance will be
**Distance ={(u**, where “u” is the speed of the boat in still water and “v” is the speed of the stream.^{2}-v^{2}) * t} /2v - A boat or swimmer covers a certain distance downstream t1 hrs and returns the same distance upstream in t2 hrs. If the speed of boat or man in still water is given by = Y ((t2+t1)/(t2-t1))km/hr

- If a boat travels a distance downstream n “t1” hrs and returns the same distance upstream in “t2” hrs, then the

Boats and Streams Questions and Answers **With Detailed Explanation** – Quantitative Aptitude

## Boats and streams

Your answers are highlighted below.

Question 1 |

A man rows downstream at 20km/hr and rows upstream at 15km/hr. At what speed he can row in still water?

17.5 km/hr | |

18 km/hr | |

20.5 km/hr | |

22km/hr |

Question 1 Explanation:

**Answer: Option A**

__Explanation:__

Speed in Still Water = (1/2) * (Speed Downstream + Speed Upstream)

Speed Downstream = 20km/hr

Speed Upstream = 15km/hr

Therefore, Required Speed = (1/2) * (20 + 15)km/hr

=(1/2) * 35

**Speed he can row in still water = 17.5km.hr**

Question 2 |

How long will it take to row 20km upstream if one can row 10km in 10mins in still water and the same distance in 8mins with the stream?

12 min | |

13.33 min | |

24 min | |

26.67 min |

Question 2 Explanation:

**Answer: Option D**

__Explanation:__

Let x be the speed of man in still water and y be the speed of stream.

Therefore, Speed of man(x) = 60km/hr

It takes 8min to travel 10km in the stream, Therefore it's going downstream.

Speed of Downstream = 75 km/hr

X + Y = 75

60 + Y = 75

Y= 75 - 60

Y= 15km/hr

Note that Question is about upstream.

X - Y = 60 - 15 =45km/hr

Speed = Distance / Time

Time = 20/45 hrs = 5/9hrs

**Ans = 26.67min**

Question 3 |

A man's speed with the current is 5km/hr and the speed of the current is 2.5km/hr. The man's speed against the current is:

8.5 km/hr | |

9 km/hr | |

10 km/hr | |

12.5 km/hr |

Question 3 Explanation:

**Answer: Option C**

__Explanation:__

Man's Rate in still water = (15 - 2.5)km/hr = 12.5 km/hr

Man's Rate against the current = (12.5 - 2.5)km/hr = 10km/hr.

Question 4 |

A boat running downstream covers a distance of 16km in 2 hours while for covering the same distance upstream, it take 4 hours. What is the speed of the boat in still water?

4km/hr | |

6km/hr | |

8km/hr | |

10km/hr |

Question 4 Explanation:

**Answer: Option B**

__Explanation:__

Rate Downstream = (16/2)km/hr = 8km/hr

Rate Upstream = (16/4)km/hr = 4km/hr

**Therefore Speed in still water = (1/2) (8 + 4) = 6km/hr**

Question 5 |

The speed of a boat in still water in 15km/hr and the rate of current is 3km/hr. The distance travelled Downstream in 12mins is:

1.2km | |

1.8km | |

2.4km | |

3.6km |

Question 5 Explanation:

**Answer: Option D**

__Explanation:__

Speed Downstream = (15 + 3)km/hr = 18km/hr.

**Distance Travelled = (18 * (12 /60))km = 3.6 km.**

Question 6 |

A person can swim in water with a speed of 13km/hr in still water. If the speed of the stream is 4km/hr, What will be the time taken by the person to go 68km Downstream?

2.5 hours | |

3 hours | |

4 hours | |

3.5 hours |

Question 6 Explanation:

**Answer: Option C**

__Explanation:__

Downstream Speed = (13 + 4) km/hr = 17km/hr

To Travel 68km downstream.

**Time Taken = 68/17 = 4 hours**

Question 7 |

A boat is moving 2km against the Current of the stream in 1hr and moves 1km in the direction of the current in 10mins. How long will it take the boat to go 5km in Stationary water?

1hr 20mins | |

1hr 30mins | |

1hr 15mins | |

30mins |

Question 7 Explanation:

**Answer: Option C**

__Explanation:__

Downstream = (1/10) * 60 = 6km/hr

Upstream = 2 km/hr

Speed in still water = 1/2 * ( 6 + 2) = 4km/hr

Therefore, the time taken by the boat to go 5km in stationary water = 5/4hrs => 1*(1/4) = 1hr 15mins

Question 8 |

A Motorboat, whose speed in 15km/hr in still water goes 30km downstream and comes back in a total of 4hrs 30mins. The speed of the stream (in km/hr) is:

4 | |

5 | |

6 | |

10 |

Question 8 Explanation:

**Answer: Option B**

__Explanation:__

Let the speed of the stream be x km/hr. Then,

Speed Downstream = (15+x)km/hr

Speed Upstream = (15-x)km/hr

Therefore,

9x

^{2}= 225

x

^{2}= 25

x = 5 km/hr.

Question 9 |

In one hour, a boat goes 11km/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 |

Question 9 Explanation:

**Answer: Option C**

__Explanation:__

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

Question 10 |

A man can row at 5 kmph in still water. If the velocity of current is 1 kmph and it takes him 1 hour to row to a place and come back, how far is the place?

2.4 km | |

2.5 km | |

3 km | |

3.6 km |

Question 10 Explanation:

**Answer: Option A**

__Explanation:__

Speed Downstream = (5+1)kmph = 6 kmph.

Speed Upstream =(5-1)kmph = 4kmph.

Let the required distance be x km.

Then, (x+6)+(x+4) = 1

=> 2x + 3x =12

=> 5x = 12

Therefore

**x = 2.4km.**

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