10 Coins Puzzle || Logical Interview Puzzles

Interview logical puzzles are a type of problem or challenge that is designed to test a person's critical thinking, problem-solving, and reasoning skills. These puzzles are commonly used in job interviews for positions that require analytical and problem-solving abilities, such as software development, data analysis, and management roles.

Problem: You are blindfolded and 10 coins are placed in front of you on the table. You are allowed to touch the coins but can’t tell which way up they are by feel. You are told that there are 5 coins heads up, and 5 coins tails up but not which ones are which. How do you make two groups of coins each with the same number of heads up? You can flip the coins any number of times.

This puzzle was asked in many companies and other interviews since these kinds of puzzles help to find the logical thinking ability of the candidates.

Solution:

here is the correct way to approach 

the logic is => Make 2 groups with an equal number of coins. Now, flip all the coins in one of the groups. flipping means turning the coin head to tail and tail to head.

Here is how this will work with a couple of examples? So initially there are 5 heads and 5 tails, so suppose you divide it into 2 groups there are multiple possibilities.

I will consider 2 possibilities, where the logic holds valid.

Case 1:

assume that group P1 has coins with 2 heads and 3 tails: H H T T T and group P2 has coins with 3 heads and 2 tails: H H H T T

Now P1 will be flipped, after flipping, P1 has 2 tails and 3 heads: T T H H H

now we can clearly see that number of heads in group 1 is equal to the number of heads in group 2. In this example, I have selected group 1 to flip, but you can choose any group to flip still we can achieve the result.

P1(Heads) = P2(Heads)

Case 2:

In this case, assume that group P1 has coins with 1 head and 4 tails: H T T T T and group P2 has coins with 4 heads and 1 tail: H H H H T

Now when P1 is flipped, we can see that number of heads in group 1 is equal to the number of heads in group 2.

P1: H H H H T

P1(Heads) = P2(Heads)

In this way we can make sure that number of heads is equal in both groups logically, using these simple steps.

Note: there is only one case which will not guarantee that number of heads is equal in both groups, that is when the number of heads in any of the groups is 5 and if you choose the same group to flip. In this scenario, all coins in both groups have tails up which is not the expected output. I would suggest you remember this scenario.

Watch the below video for a detailed Explanation