Calculation Races

Mental versus written multiplication

My class and I were undertaking a Number Talk. The question we were using was ’19 X 24′. I hoped many children (mixed ability Year Five) would use a mental method or jottings (partitioning, rounding & adjusting and so on).

However, over 90% of the class used a grid method or expanded column multiplication. Nothing wrong with that, except the focus we’d been having on mental methods and not always defaulting to a written method. We listened to how children had arrived at their answers and then discussed which were the most efficient. As a class, we then solved both 19 X 28 and 19 X 35 using rounding (20 X 28) and partitioning (10 X 35 added to 9 X 35) to remind them of the available less formal/mental / jotting methods available to them.

In order to win over the remaining doubters I still had in the class, I set the children a challenge. They’d solve a question using only mental methods, while I tried to answer it as a written method on the classroom whiteboard. Although I wanted to prove the mental method was the quickest, I still tried really (really, really) hard to do my method quicker than the class. However, I ‘lost’ all three times (19 X 56, 19 X 45 & 29 X 34). I’d only got beyond setting up the method and doing the first part of the calculation.

The class won over!

This article first appeared in our free UKEdMagazine, which is available to view by clicking here.

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The Editorial Account of UKEdChat, managed by editor-in-chief Colin Hill, with support from Martin Burrett from the UKEd Magazine. Pedagogy, Resources, Community.

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