A brainteaser reportedly used during interviews for Harvard University has stumped 90 percent of people who attempt it.

The image, shared on social media, shows the university's letterhead with a mathematical problem written in red and black ink.

The question asks, 'if there are seven men with seven wives and each man and each wife have seven children, what is the total number of people?'

But unlike most brainteasers, this one has two answers. 

The interview puzzle first hit the internet in 2021, but has since resurfaced online to stump another group of players who have shared different answers. 

The answers ranged from as low as 21 people to as high as 448, with one person even claiming the answer could be much higher, citing 700 people, although they did not explain their reasoning.

'This is all word play,' one person commented on the post. 'There are several answers and not one is wrong unless you don't get the math right. 

One user said it comes down to how you interpret the question - if each man has one wife, the correct answer would be 63, but if you look at it as each man has seven wives, the answer is 392.

'This is ambiguous, which I guess is the point,' said one user, adding: 'But let's assume that there are just seven couples (seven men and seven wives), which equals 14 people. 

'Each couple had seven kids, so that is 7x7=49 kids. Add 'em up and it is 63 people.'

Assuming each man has seven wives, to get to 399 people, you would multiply seven by seven to get 49 wives and add that number to seven men. 

Then, if each of the 49 wives has seven children, that's 343 and if each man has seven children, that's 49, equaling 392 people.

Mathematical brain teasers are important because they encourage people to analyze information and consider the answer from different points of view.

It reveals how they break down problems into smaller, manageable steps and whether they utilize out-of-the-box thinking.

But if you were one of the many people who were off the mark, you should be reassured that you're not alone. 

It also unclear if the brainteaser came directly from Harvard, DailyMail.com has contacted the university.