What do I want children to do when they are challenged to add numbers together? I believe too many children go straight to a column method, failing to look at the numbers and ask the crucial question, ‘Can I do it in my head?’
A child who really understands the properties of 45 (and all other 2 digit numbers) would hopefully do the following! –
- 45 + 27 – partition both numbers, making 60 + 12 = 72
- 45 + 19 – round the 19 to 20, add 20 then subtract 1, 45+20-1 = 64
- 45 + 7 – count on 7 from 45, 45 + 7 = 52
- 45 + 35 – number bond 35 with the 5 then add the 40, 35+5+40 = 80
45 + 46 – double 45 then add 1, 45 + 45 + 1 = 91
The most successful way that I’ve found of promoting this approach to mental maths is through a mnemonic called RAPA CODA NUMBO. This is a quick and fun idea to easily remember the five key mental strategies. Initially, children learn the names of the strategies through chanting them (often introduced by a ‘maths rapper called RAPA CODA NUMBO – maybe the teacher wearing shades and a baseball cap!!!) and then, over a series of lessons, the five strategies are introduced individually, and practised with appropriate numbers.
Find out more about Rapa Coda Numbo in action, and many more helpful ideas, on my Mental Calculation course on 29th January at the Village Hotel in Warrington!