Stage 7: Short and Long Multiplication
The recording is reduced further, with carry digits recorded below the line for calculations using TU x U.
Children who are already secure with multiplication for TU × U and TU × TU should have little difficulty in using the same method for HTU × TU. This formal algorithm will be taught from year 5. Most children will be secure in using this method to multiply up to 4 digit numbers by 2 digit whole numbers by the end of year 6.
Again, the importance of recognising the place value of the digits involved will be stressed. e.g. 20 x 6, 20 x 80 and 20 x 200; the relationship between 2 x will inevitably be utilised.
As an intermediate step, each stage of the multiplication can be explicitly recorded in an expanded form to show the separate products. These intermediate products are then totalled at the end, as in the standard compact algorithm.
Please click on the link below to watch the videos;
modelling the 3 digit by 2 digit (expanded brackets) multiplication strategy.
multiplication 3 digit by 2 expanded brackets
modelling the 3 digit by 2 digit long multiplication strategy.
multiplication 3 digit by 2 digit long multiplication