Long Multiplication

In this dyslexia blog article there are some tips and advice on long multiplication.

Being able to recall basic multiplication facts is essential for success with long multiplication, therefore it is crucial you make sure your child practices their times tables on a regular basis. Games are a good way to motivate them to learn them !!

Students who have dyslexia will often have a weakness in their working memory. As a result it may be difficult for them to rely solely on mental calculations when solving math problems.The dyslexic student may often forget what they are doing and lose their place . In long multiplication ,of course,there is more of a risk that there will get muddled up since the numbers that they are dealing with are bigger.

When they are are doing long multiplication problems teachers and parents should encourage children to write down every step, including carrying numbers.They should also preferably use scrap paper to help them in their calculations.

Common errors made :

Students make mistakes because they haven’t kept their columns straight. Make sure they line up their numbers correctly and also encourage correct spacing. It is advisable to use squared paper at all times for maths calculations to prevent this problem.
Unfortunately sometimes teachers don’t leave enough space for workings out on worksheets and test papers and this creates problems !!

Forgetting to ‘carry’ numbers A good way to remember the carry number is to write it in a circle.

Forgetting to write down a zero eg :

110
x69
990
660 should be 6600
=1650 ( answer should be 7590 )

You could consider teaching your child alternative methods to solve long multiplication problems. One such method is long multiplication using key facts. This method is recommended by Steve Chinn who is one of the leading experts in the area of dyscalculia. With this method your child only needs to know how to double and half numbers and multiple by 10 to get the correct answer.

Long Multiplication using key facts

E.g 78 x 17

1) First set up an easy multiplication table with the key facts :


1 x 17 = 17
2 x 17 = 34
5 x 17 = 85
10 x 17 = 170
20 x 17 = 340
50 x 17 = 850
100x 17 = 1700

1x 17 is easy to find = 17.
To get 2 x 17 just double 17.
After workout 10 x 17 = 170 .Now you can easily find 5 x 17 – just half 170. ( 85 )
For the answer to 20 x 17 double 170 .
100 x 17 is easy just add a zero to 170 ( 10 x 17=170).
For 50 x 17 half the answer to 100 x17 = 1700 ie 850.

2)After find the easy numbers ( or partial products ) in 78 .

78 = 50 + 20 + 5 + 2 + 1

3) After add up these partial products :
50 x 17 = 850
20 x 17 = 340
5 x 17 = 85
2 x 17 = 34
1 x 17 = 17

Answer 78 x 17 = 1326

In Turkey however unfortunately some teachers are reluctant to teach alternative methods of doing maths calculations. Also this method does require more space on the paper for the workings out. In many cases worksheets and test papers provide little space for students to use .It is assumed a lot of workings out will be done mentally. Teachers here in Turkey need to try to be more flexible in their approaches in order to accommodate all children. I would recommend everyone to look at Steve Chinn’s books for more ideas regarding maths.