Tough Interview Logical Questions With Answers

Tough Interview Logical Questions With Answers
Nowadays Logical Puzzles are asked in the interviews. If you can going for an interview in a software development company then it is definite that some logical puzzles will be asked from you. Sometimes Quick Interview Questions will be asked in the interview. However here I am posting some of the tough interview questions being asked in many companies like Flipkart, Google, Microsoft, Amazon, Infosys, etc.
Anyway here are I am putting some of the tough interview questions which are being asked as screening of many IT companies. I will keep adding new questions in the same thread. Answers to these tough interview questions are given at the end of this post. To avoid any spoilers, I have hidden the answers. Do select the text between numbers to see the solution to a specific interview question.
I mentioned that these are the interview questions being asked in Information Technology(IT) companies. In typical IT companies different people even if working at the same level/designation may have different salaries. So it is not considered good to discuss one's salary with another person. The first interview question is based on salary.
1. Four employees of a Software company are sitting together and they want to find out their average salary anyone knowing any other person's salary. How this can be done?

The next question was asked by one of my friend in Google Interview
2. There are seven sisters in a home in a remote village where there is no electricity or any gadget.
Sister-1 is Playing Sudoku
Sister-2 is Washing clothes
Sister-3 is Playing Chess
Sister-4 is Reading Novel
Sister-5 is Cooking
Sister-6 is Gardening 

what is Sister-7 doing?

Developing software requires a lot of logical thinking as well as Mathematically knowledge. The following question is being asked in Software development companies like Microsoft or Google where Math skills are also required along with logical thinking.

3. Interviewer says that I can prove why 1 = 2
a. Lets say y = x
b. Multiply through by x, xy = x2
c. Subtract y2 from each side xy - y2 = x2 - y2
d. Factor each side y(x-y) = (x+y)(x-y)
e. Divide both sides by (x-y) y = x+y
f. Divide both sides by y y/y = x/y + y/y
g. And so... 1 = x/y + 1
h. Since x=y, x/y = 1 1 = 1 + 1
i. And so... 1 = 2
How is this possible?

Sometimes one can logically reach different answers depending upon how you read the statement of the question. Here is one interview question which not only can be answered differently but also be explained logically. I have explained both the answers to this interview question.
4. Mr. Manish wishes to cross the Thar desert. It requires 6 days to cross the Thar desert. One man can only carry enough food and water for 4 days. What is the fewest number of other men required to help carry enough food for Mr. Manish to cross?

Let us try to find a general solution to the above problem.
5. What about if it takes 18 days to cross the desert. You can only have 12 days of the food supply. You can take a maximum of two people along you to help you to cross the desert.


Below is hidden answers to these Brain Teasers. Select the text between the numbers to the lookout at the corresponding answer.
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1. If the first time one comes across this puzzle, it looks tough interview question. However, if you thinking logically you can find the average salary of four employees without anyone knowing each other's salary. This solution is not limited to four people but can be applied to N people who want to find out their average salary. To do this 1st person will add a random number to his/her salary and pass the total to the next person. The second person will add its own random number and then pass it to the 3rd person and so on. The last person will pass the total after adding his/her own random number to the 1st Person. Now they will do the reverse process by subtracting their random numbers from the total and then passing it to the next person. When everyone has subtracted their own numbers the total represents the sum of their salaries which when divided by N will give their average salary.

2. At first glance, this question looks like how come we can know what is the Sister-7 doing? However if one reads that they are in a remote village where there is no electricity or gadget then immediate logical thought comes that there has to be one activity that cannot be performed by a single person. So the Sister-7 is playing chess with Sister-3.


3. Step [e. Divide both sides by (x-y)] is wrong here. As x=y, so x-y = 0; Dividing anything by 0 leads to infinity which voids the equation and leads to the wrong result.

4. The first answer which most people will conclude logically is TWO people. All three start with 12 days of food. After 1st day 3 days of food is consumed and  1 person returns back with 1-day of food and the remaining two people will start with 8 days of food. The next day 2 days food is consumed and the second person goes back with 2 days of food and Manish goes to cross the Thar desert with 4 days of food.
Another answer to this problem can be ZERO people as the puzzle statement does not mention that Manish has to take the minimum days possible to cross the Thar desert. Mr. Manish alone can carry food out into the desert and leave it, then return home for more food, then go out further and leave it, etc., until he has enough stored to complete the journey. Each day, Manish leaves home with 4 days' worth. He starts the ordeal by taking 2 days' worth of food out to the 1/6th point and returns home since he uses 1 day's worth to get there and 1 to get back. Next, he does the same thing, now having 4 days' worth stored there. On the next trip out, he ends with 7 days' worth there, since he doesn't return home again. Then he uses 4 of the 7 to store 2 at the 2/6th point and return to the 1/6th point, where he had left 3. Lastly, he takes those to the 2/6th point, giving him the 4 he needs to go 4 days to finish the desert crossing.

5. To solve this kind of problem one has to start from the end. As in the end, one needs to have 12 days of food then move backward with your helper. I will leave it to readers to solve this puzzle and comment on their answers.
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Here is the answer to the 15th Brain Teaser Question of the post titled "Out of Box Thinking Fun Brain Teasers with answers to Challenge your Mind ".
I have hidden this answer to avoid any spoiler. Do select the text below to read the answer. 
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The answer to this Riddle is COCONUT. If you feel hungry a Coconut has a part that you can eat. If you feel thirsty a coconut has its juice contents which have high ions for better re-hydration. When you feel cold there is a part of a coconut that is good for burning and it turns into charred coal when totally burnt.

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