Thursday, 10 January 2013

We had a good discussion on the teaching of a written method for division in a school I was in earlier this week.

### Chunking method for division

‘Chunking’ has been encouraged in schools over the past 10-12 years (it was recommended in the NNS and Primary Strategy), as it requires genuine understanding of the process and is a useful way of recording repeated subtraction in a written form.

However, the report ‘Good practice in primary mathematics: evidence from 20 successful schools’published by Ofsted in November 2011, found that pupils made more errors using this method than the old ‘bus-stop’ method for long and short division.

Interestingly, a Y6 teacher at the school agreed and had been using the bus-stop method in the past few years as she found that the many stages of chunking were causing her pupils difficulties. Perhaps the bus-stop is a method that does work, and the fact that mathematically it is a weak algorithm to model or explain may not matter to the high ability children using it.

This is a key point though – it is only suitable for more able pupils. The problem with it is when it is introduced to younger or less able children with a poor grasp of place value, partitioning numbers, division facts etc. This is probably why some schools leave long division out of their primary curriculum, letting secondary schools introduce it when the pupils are ready.

A third method, using factors, is another approach to consider for more able pupils and certainly worth exploring. For this method, 432÷16, for example, can be broken down into two divisions using the factors of 16. Look at the example below: 423÷8=54, 54÷2=27, so 432÷16=27. Obviously 16 could also have been divided by 4 twice.

Let me know what you think. Is ‘chunking’ just too clunky as a written method? Is there a better alternative? More importantly, is there a better name than bus-stop?!

#### Using factors to divide

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