Summary
Having dyscalculia, or other specific maths difficulties, can make the long multiplication written method very challenging to understand and correctly carry out. A secure understanding of the process can be facilitated by using manipulatives and pictorial representations first of all. This is really important in helping to make the individual parts of the calculation clear, before just working abstractly with the numbers.
The long multiplication method is used when multiplying two numbers which both have two or more digits. Before beginning work on this method, it is important that a child is secure and confident in using the written method for short multiplication (multiplying a number by a single digit- see previous video here – https://dyscalculianetwork.com/short-multiplication-for-learners-with-dyscalculia/
Whilst learning to use the long multiplication method, a multiplication square is a very valuable resource, to remove anxiety about recalling times table facts and to reduce the stress on working memory. This helps to ensure that the focus remains on understanding the process.
Using Cuisenaire rods, a calculation such as 14×12 can be shown by making 14 (with a 10 rod and a 4 rod) twelve times. We can then separate the column of 14s to show a block of 14×10 and a block of 14×2. In this way, we see that the calculation can split into four individual parts:
10×10=100 and 4×10=40
2×10=20 and 4×2=8
Then we can add these individual answers together:
100+20=120 and 40+8=48 So altogether 120+48=168
Place value tens and ones blocks can be used instead of Cuisenaire rods, ( ) or online resources provide another alternative: https://mathsbot.com/manipulatives/rods
However, we need a lot of manipulatives to represent long multiplication in this way, so moving to a pictorial representation, such as the grid method, means that the Cuisenaire rods can instead be drawn as rectangular blocks.
The final step is to use the abstract written method. When working through this method, it can be useful to use a blob of Blu-Tack to cover the digits not currently being used. So when working out 14×12, we would begin by multiplying 14 by 2, so the Blu-Tack would cover up the 1 in the number 12. Once this in completed, we can move the Blu-Tack across to cover the 2, so we can multiply 14 by the 1 in the tens place. Moving the Blu-Tack to the cover the 2 ones also reminds us that we need to record a zero in before beginning this part of the calculation, as we are working now in the tens column.
