Cool Brainteasers

Who is the coin thief puzzle

Here is a new puzzle for you to solve. A coin is stolen, can you find out who the coin thief is?

Rammy has a gold coin. One day, his 4 friends, Alex, John, Mark and Niki came to his house for the party. Next day, Rammy found out that his gold coin was missing. He suspects that one of his 4 friends may have stolen it.

He calls each one and gets the below response. If only one of them is telling the truth then, can you figure out who the thief is?

Alex – I think John stole your coin.

John – I didn’t steal it.

Niki – I think Alex stole your coin.

Mark – I didn’t steal it.

Who is the coin thief?

As only one person is telling the truth. So, there can be 4 four scenarios that one of these statements can be True and other 3 should be False.


Here are some more similar brainteaser which you can also try using below method and see if this works. Who is the thief? and Who’s Telling the Truth?

Answer: Mark is the Thief.

Let’s try decoding each statement now. Simple way to solve this type of brain teaser is to assume that one of these statements is true so add NOT in other statements.

Scenarios1 –> Alex – I think John stole your coin. –> If this is true, then it makes John’s statement as False since john is the thief however it also makes Mark(I didn’t steal it) statement as true which means, this scenario cannot happen since it will make both John and Mark as thief.

John – I did steal it.

Niki – I think Alex didn’t steal your coin.

Mark – I did steal it.

Scenarios2 –> John – I didn’t steal it. –> If John is telling the truth which makes Alex’s statement false. Just assume that the other 2 statements are also false, that means Alex cannot be a thief and to make the last statement to be false that means Mark is the thief.

Alex – I think John didn’t steal your coin.

Niki – I think Alex didn’t steal your coin.

Mark – I did steal it.

Let’s check other 2 scenarios as well to confirm that only scenario2 can be the actual one.

Scenarios3 –> Niki – I think Alex stole your coin. –> If Niki is telling the truth which means Mark is also telling the truth so this cannot be the scenario. This will again make both John and Mark as thieves.

Alex – I think John didn’t steal your coin.

John – I did steal it.

Mark – I did steal it.

Scenarios4 –> Mark – I didn’t steal it. –> If Mark is telling the truth then one of the other 3 can be the thief. So when we add NOT, We see that both Alex and John’s statements contradict each other.

Alex – I think John didn’t steal your coin.

John – I did steal it.

Niki – I think Alex didn’t steal your coin.

P.S. Please add this post link as source credit if you want to use this brainteaser or, if you want to repost it. Thank you



By Kumar

Hi All, I am Ramesh Kumar, author of this blog. I am an IT engineer. I love puzzles and riddles so I decided to publish the same for others like me. If you like puzzles then do subscribe to my email listing. You can also follow me through the website Facebook page . If you like to contact me then use the contact page form, I will reply to your emails ASAP. Thanks

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