If you've ever been curious about what it takes to land a job at Google, it appears that problem-solving abilities and 'thinking outside the box' are crucial for acing an interview. TikTok creator Tanya Zakowich, known as @pinkpencilmath on social media, has revealed that Google once tested its job candidates with a brainteaser during job interviews - and wouldn't hire anyone who couldn't solve it.

However, in 2013, it's believed that Google reduced the use of such questions after their former head of human resources told the New York Times that they couldn't "predict anything" and were mostly used to "make the interviewer feel smart".

In her video, she shares: "If you don't know the prisoner hat riddle, you're going to love this one. It's a super classic brainteaser that was commonly asked in job interviews at Google."

She then describes the riddle: "There were four prisoners on a staircase all facing the same direction. A brick wall separates prisoner 4 from the rest."

She says prisoner 1 can see prisoners 2 and 3, while prisoner 2 can only see prisoner 3 and prisoners 3 and 4 cannot see anyone, reports the Mirror.

She added: "All four prisoners are wearing hats. They are told there are only two black hats and white white hats. However, they do not know the colour of the hats they are personally wearing.

"The prisoners were told to shout out the colour of the hat they're wearing as soon as they know what colour it is."

With this information, she poses the question: "Who is the first person to shout out correctly - and why?"

The prisoners were strictly instructed that they could not turn round to see the others, rearrange their formation or remove their own hats.

One individual pondered over the puzzle saying: "Prisoner two. If both prisoner two and three were wearing the same hat, one would have known that he was wearing the other hat. But since he didn't, two knows that."

A second person commented, suggesting: "Two as he can use one's silence to infer that two and three have different colour hats. Since two can see three then two must be the opposite colour of three."

Yet another reasoned: "Four because he knew no one was looking at him so he took his hat off to look."

Another person said: "I used to give this riddle to my math students all the time. It's two because one didn't say anything so they know they're different from three."

According to Puzzles and Riddles, the answer is indeed prisoner two.

Their reasoning states: "If prisoners 2 and 3 had the same colour hat on, prisoner 1 would have know immediately that his hat was the other colour (there are only two hats of each colour).

"Since prisoner 1 was silent, prisoners 2 and 3 must have different coloured hats. Prisoner 2 realised this and knew that his hat was not the same colour as prisoner 3, therefore his hat must be black!".