# 243 – My new favourite number

I’ve got a new favourite number – 243.

Why is it my favourite? It’s not because it’s 3 to the power of 5, although that does make it special.

To find out why 243 is my new favourite number, divide 1 by 243:  1 ÷ 243

OK, to save you doing the maths, the answer to 1 ÷ 243 is:

0.004115226337448559 …

which I think is pretty cool.

Now, I’d like to say I discovered this little gem for myself, but I’d be lying. I stumbled across this little snippet whilst reading:

Richard Feynman was a great physicist, but this book is not just about physics, its a fascinating and amusing tale of an extraordinary life. You might enjoy reading it, too.

Teaching Tips

How could you use this in a maths lesson?

You could just as your pupils to divide 1 by 243, but that’s quite hard.

But introduce them to division by factors – so to divide by 243, you can split 243 into factors and divide by those.

As 243 = 35 you could divide 1 by 3, then divide that answer by 3, then divide that answer by 3, then divide that answer by 3 and then divide that answer by 3 but it would be much quicker – and much more interesting – to do 1 divided by 9, then divide that answer by 9, then divide that answer by 3 (as 243 = 9 x 9 x s)

Go on, grab a scrap of paper and have a go yourself!