# Problem analysis and summary: classical logic questions "how to use less than 15L of water, 3 liters of water from the pond with 2 kettle"

CSDN University Club Interview questions

Liang wood water Chen

GraduateBeijing University of Posts and Telecommunications

In January 8, 2015, the club launched"How to use less than 15L of water, 3 liters of water from the pond with 2 kettle"Challenge the classic logic interview questions, there are nearly 100 members to participate in online interaction, and put forward a variety of new ideas. In the traditional two barrels each pour ideas, there are a lot of students proposed the principle of buoyancy, filling principle, method of marking, pulley, lever principle, free falling principle, time principle, combined with the mathematical knowledge, try all kinds of different solutions. It can be said that all roads lead to Rome! The event and a time to see the students thinking about the problem of diversity and differences in thinking.

In this order and workable ideas and carries on the contrast analysis, to find the optimal solution, and tries to through the phenomenon eventually see the essence.Hope that every person in the process of discovering the problem solving process, can be able to break, dare to innovate, dare to try new methods. You will find that you can have a harvest in every way that leads to Rome, which is far better than a fixed result, and can enrich your experience and help you grow.

### Original title:

If there is a pond, there is an infinite number of water. The existing 2 empty water bottles, the volume of 5 liters and 6 liters. The problem is how to get 3 liters of water from the pond with these 2 water bottles.

### Methods using 1: 2 barrels of water capacity difference

This is the most basic way to achieve, without the aid of any external tool, do not consider the shape of the pot is the rule, not to consider the use of water saving. The method accords with the original title too observant of conventional standards..

### Method 2: marking method

It is obtained by using the method of marking the water height by marking the 1L height of the bucket wall (inner wall or the outer wall, a wooden stick), and obtaining the final 3L water for 3 1L water. In case the outer wall is marked, the bucket needs to be transparent or semi transparent; the diameter of the barrel can be allowed to enter into the case of the mark.

### Method 3: buoyancy principle

It is similar to the measurement method of "Cao Chong", using 1L water in the water in the water, the way to make a mark on the outer wall of the barrel. This method does not require the use of any external tool, the shape of the bucket is not required, the overall water consumption. The bucket can float in the water, if it is filled with water.

### Method 4: filling principle

It imitates the story of "the crow drinking water", the use of non absorbent filler, access to 3L of water. The method needs to be realized by external props, and it is feasible in theory.

### Method 5: hole method

This method obtains 3L water by means of a hole in a hole with the same diameter as the same as the bottom of the barrel.

Although the method is novel and unique, it belongs to the destructive one time solution, although the theory is feasible, but it is not advocated in practice.

### Method 6: leverage principle

This method obtains the capacity of 3L water by calculating and adjusting the balance of lever. With external tools, and with mathematical calculations to obtain the desired results. Process of mental and physical coordination.

### Method 7: time principle

This method is used to measure and calculate the flow velocity and obtain the required 3L water. Although theoretically feasible, but the actual operation is not strong, is an ideal solution.

### Method 8: evaporation principle

This method uses the water's volatility principle to obtain the required 3L water by observing and measuring the time. Although theoretically feasible, but the environmental requirements are too high, the actual operation is not strong, is an ideal solution.

### Analysis- > view all reply and answer thinking

Through the research on the method of all the students, it is found that the optimal method is still the best.Method 1.

The principle of 15L is 5+5-6+5-6=3, the principle of 18L is 6-5+6-5+6-5=3. If you don't use any tool, it's the best way to do it. Because the volume of the two containers is the largest is 11, adjust the position of any two number is more than 11 or less than 0. So if it is strictly in accordance with the original intention of the answer, there will be no unexpected answer.

But the highlight of the event is that it inspires the students' divergent thinking and innovative thinking, jump out of the inherent thinking, and can be combined with other theories of common sense and life, the courage to express their views and discuss interaction with others.

Hope that every person in the process of discovering the problem solving process, can be able to break, dare to innovate, dare to try new methods. You will find that you can have a harvest in every way that leads to Rome, which is far better than a fixed result, and can enrich your experience and help you grow.

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2015-01-29
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2015-11-26
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Eleven
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One

Zhangfengzhang123

GraduateHubei automobile industry

By using the 6L bucket to take the 6L of water, into the 5L of the bucket, left 1L of the water, the 6L of the bucket in accordance with the standard of this 1L cutting, so that it becomes a bucket of 1L, and then through the 1L of the bucket to the 5L three times

Shared water 8L

2015 2, 2, 13:28:07

Liang wood water Chen

GraduateBeijing University of Posts and Telecommunications

This idea is tailored to create new styles. If the bucket is made of mud or wood, how do you cut it? It will come apart.

2015 3, 2, 09:58:06

U011003276

StudentChengdu Information Engineering

6L filled into the 5L, the 5L vacated, 6L 1L into 5L, then filled with 6L, again to with H2O 1L 5L container filled with, such 6L container is equipped with a 2L water, 5L container will be empty 6L container 2L water into a 5L container, finally filled with water 6L container will 5L container filled with, 6L vessel left the 3L water the

2015 12, 3, 19:15:16

Yxyyg

StudentUniversity of Electronic Science and technology

6-5=1 (6 in 5, left 1. 5 empty, 1 in 5.

5-1=4 (5 at this time, 4)

....

4-1=3

2015 24, 3, 22:57:38

Liang wood water Chen

GraduateBeijing University of Posts and Telecommunications

Why not think of, 5L to 6L barrels full of bottled water way? That total water will also save 3L.

2015 25, 3, 13:36:37

RLib

StudentGuangdong University of Technology

So all become? It might as well assume that small changes in the surface of the pond can be seen, the 5 liters of water to go back, leaving 1 liters, the observation of the pond water changes to remove the remaining 2 liters.

2015 13, 4, 19:49:12

Rococo 258

StudentAnkang University

First with 5L bucket filled with water, pour into the 6L, at this time there is a 6L 5L water, but also poor 1L. And then filled with 5L bucket, poured into the 6L bucket and then 6L bucket is full, the bucket 5L left 4L water, drained 6L barrels of water, the bucket 5L 4L water poured into the bucket 6L. 6L barrel with 4L water, still 2L full. Meanwhile, the 5L barrel full of water, poured into the 6L bucket. 6L bucket full, bucket 5L just left a 3L water.

2015 18, 4, 00:04:31

No dirty eyes

StudentWuhan Textile University

Put the 5L barrel inside the barrel of 6L. 6L filled bucket, 1L water, but in 5L bucket, three times in a row get 3L water, water 3L

2015 17, 7, 16:06:19

Chaolin1994

StudentSouth China University of Technology

The change of water quantity in 2 water bottles:

50
5
55
46
40
4
54
36
30

2015 7, 9, 19:02:13

Alice_ full min

StudentHunan foreign economic

1 5L buckets, 6L empty bucket.

2.5L water all into the 6L of the bucket, at this time 5L, 0L

3.5L barrels full of water, then the water to fill the barrel of 6L, 5L and 4L have 6L barrels of water, water bucket 6L

4 6L bucket of water poured into the 5L 4L water all into the 6L 5L, then 0L 6L water, 4L bucket of water

5 5L buckets, 5L barrels of water into the bucket filled with 6L, 3L, 5L at 6L water water bucket, 6L bucket

This 5L bucket is the water we need.

October 30, 2015 18:37:10

Xuan month ice Ling

StudentShanghai Jiao Tong University

Impossible, unless......

November 26, 2015 11:46:12