## Fibonacci Sequences – the Golden Rule about the Golden Ratio, which we just found out…

We just found out something new….

It turns out that** if you take the first ten terms of**** any Fibonacci sequence, the sum of those 10 terms is equal to the 7th term multiplied by 11.** Got it?

OK, let’s unpack that. Here’s the most basic Fibonacci sequence:

1,1,2,3,5,8,13,21,34,55

If you plug these into your head/calculator, you will find that the sum of these 10 terms is **143**.

Much quicker: take the 7th term (in this case 13), multiply that by 11 and you get, as if by magic… **143**.

And it works for any Fibonacci sequence. Let’s imagine one with bigger numbers starting with (to pick a number completely at random) 42:

42, 42, 84, 126, 210, 336, 546, 882, 1428, 2310

So we add all the terms up on a calculator and get **6,006**.

Now, much quicker, jot down the 7th term (here: 546), multiply it by 11 and, hey presto: 546×11=**6,006**

It’s a trick you can cheerfully teach to your maths students – get them to take it home and impress their parents. Something along the lines: “hey, dad/mum, I bet I can add up a Fibonacci sequence faster in my head than you can using a calculator”.

Our thanks to the **Republic of Maths** blog that brought this to our attention, via **this video link**.

**One final note:** the covers on our (as in: Longman’s) **AQA GCSE Maths Student Books **this year were inspired by spirals. A spiral galaxy on our **Foundation sets book**, a spiral staircase on our **Higher sets book**, and a **chameleon’s tail **on our **Middle sets book **(someone must’ve been wondering what this image was?) –

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