Who developed the grid method of multiplication?

Few people disagree on the importance of being able to multiply large numbers together. However, there is much debate on the best way to do so.

Some might argue that, now that calculators are so readily available, children don’t need to learn to do this on paper (or mentally).

On the other hand, the 2014 National Curriculum advocates a move back to ‘formal written methods’.

What people might not realise, however, is that the grid method, much maligned by some as a modern trendy method that ought to be stamped out, actually has its routes in the 13th century.  The lattice method of multiplication was introduced by Fibonacci. His 1202 treatise Liber Abacii (Book of the Abacus) was the most sophisticated work on arithmetic and number theory written in medieval Europe.

His lattice method of multiplication is incredibly simple.  Here’s how to multiply 534 x 42.

First write the numbers on your grid:

Grid-method-multiplication.indd

Then multiply each pair of digits. Put the tens number on top of the diagonal line and the ones number below it:

Grid-method-multiplication.indd

Then total the diagonals (adding in carried over numbers if necessary):

Grid-method-multiplication3

The answer to 534 x 42 = 22,428

Another great way resource for teaching children mathematics is a simple deck of cards. Deck Ahoy! contains over 100 activities and games to teach primary maths skills with a deck of cards. Topics covered are not only the main operations – addition, subtraction, multiplication and division – but also fractions, statistics, time, ratios, squares and cubes and graphs.

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1 Comment

Filed under Mathematics

One response to “Who developed the grid method of multiplication?

  1. Thanks for pointing out the typo, whch I have now corrected. Apologies for the mistake. I changed the sum so that I could show how the carrying worked, and before to change the accompanying words.

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