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Long multiplication

Magnifying glass

When good mathematicians are stuck on a problem, they see if they can simplify it.

In long multiplication we break the sum down into parts that we can easily answer and then add the parts together to get our answer.

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Example 1

16 x 27 =

We don鈥檛 know our 16 or 27 times tables off the top of our head, so what can we do?

16 = 10 + 6, so to multiply by 16 we could multiply by 10 and multiply by 6 and add the answers together.

16 x 27 shown as (27 x 10) + (27 x 6) = 270 + 156 = 432

If we do the calculation the other way around we get the same answer.

27 = 20 + 7, so to multiply by 27 we could multiply by 20 (x10 and then x2) and multiply by 7.

16 x 27 shown as (10 x 27) + (6 x 27)

16 x 27 = 432

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Example 2

3126 x 47 =

Image gallerySkip image gallerySlide 1 of 10, , First we will multiply the top number by the tens (40) and then by the ones (7).
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Example 3

263 x 18=

Let's break this calculation into two parts again and then add together our two answers.

263x 18 shown as (263 x 10) + (263 x 8) = 2630 + 2104 = 4734

263 x 18 = 4734

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Activities

Activity 1

Minimal multiplications challenge

Each player should draw 6 squares as shown in the picture below.

A blank multiplication grid with 4 spaces at the top and 2 spaces at the bottom

Players take it in turns to roll a 0-6 die and place each number in one of their squares.

The aim of the game is to be the player with the smallest answer to the multiplication that they have made, so think carefully about where you place the numbers! Good luck!

Extension:

If you enjoyed the game, why not try the harder version?

Play the game again, but this time when you roll the dice, you get to place the number in the other player鈥檚 grid. The aim is still to be the player with the smallest answer at the end.

How will this affect where you place the numbers compared to the first round?

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Quiz

Using the methods from this lesson, try and answer the questions in this quiz.

You might need paper and pencil to help with your working out.

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More on Multiplying and dividing

Find out more by working through a topic