This simple sum is leading people to wildly different conclusions – here's why

A simple sum has gone viral because of the various ways people have of doing it.

The fun began when Axe Savage-Hunter tweeted: “What happens in your head when you do 27+89?”

While Twitter is so often the domain of Nazi apologism and thinly veiled bullying, this wholesome tweet gained traction purely because of the myriad ways people had of answering the question. But what is the psychology behind people’s preferred options for this bit of mental arithmetic?

We spoke to Lucy Rycroft-Smith and her team at Cambridge Mathematics, a University of Cambridge organisation developing an innovative map of school mathematics.

She's not surprised the tweet went viral.

Maths is creative, nuanced and often very visual and humans approach it in a wide variety of different ways. If you want to write a killer tweet, asking about some of those ways seems to be something of a winning formula, holding endless fascination for people!

Indeed, the team are of the opinion that the variety of methods is something to be celebrated:

One of the most powerful things you can do with children who are learning maths is to ask them to try and come up with lots of different ways of doing a sum like this – teachers will be very familiar with this sort of exercise. Helping students see which methods work in which ways, and which features of the maths they help bring forward, is a really important and fun part of maths teaching.

Dr Victoria Simms, a developmental psychologist at Ulster University, told indy100:

There are many explanations as to why people approach these types of problems differently- how we were taught when in school, our working memory capacity (how we can hold information in our minds and manipulate it), our conceptual insight around numbers (how we can quickly understand how numbers work together), how rapidly we can access number facts. When all of these things come together it may lead different people to approach a problem using a different strategy.

Clearly there are many different ways of approaching this one and no one method is more valid than another.

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