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Multiplication SmorgasbordPowerPoint Presentation

Multiplication Smorgasbord

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Multiplication Smorgasbord

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I am learning to solve multiplication problems using a variety of mental strategies.

At a smorgasbord there are lots of different foods to choose from. You now know a lot of different multiplication strategies. Now we are going to try and choose the best strategy for each question.

Work it out in your head

All the containers below hold 29 counters. How many counters are there in total?

3 X 29 = ?

There are a number of different ways we could answer this problems.

Option 1:

We could work out how many tens there are and how many ones there are then add that amount together.

3 X 20 = 60

3 X 9 = 27

60 + 27 = 87

So 3 X 29 = 87

10

10

10

10

10

10

All the containers below hold 16 counters. How many counters are there in total?

4 X 16 = ?

Option 1:

I don’t know what 4 X 16 equals but I do know that 4 X 8 = 32.

Since 8 is only half of 16 I must need to add that same amount again.

4 X 16 = (4 X 8 ) + (4 X 8)

4 X 16 = 32 + 32

So 4 X 16 = 64

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All the containers below hold 16 counters. How many counters are there in total?

4 X 16 = ?

Now let’s try a different method.

Option 2:

I’m going to try doubling and halving.

This will mean there will be twice as many groups (8) with half as many in each group (8)

4 X 16 = ?

X2

÷2

8 X 8 = 64

So 4 X 16 = 64

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Choose the best method for working out the questions below and answer.

Click again when you have worked out all your answers. A strategy for answering each of these questions will be displayed. Please note that this is only one possible solution. Your answer however should be the same.

1) 4 X 25 = ?

2) 3 X 27 = ?

3) 6 X 39 = ?

4) 7 X 22 = ?

5) 4 X 24 = ?

100, 2 X 50 = 100

81, 9 X 9 = 81

234,(6 X 40) – (6 X 1 ) = 234

154, (7 X 20) + (7 X 2) = 154

96, (4 X 12 = 48) double this amount.

Need some more practise? Try Pg34 & 35 of Teacher Tools Multiplication and Division Book Numeracy resources