Transcript Slide 1

Multiplication Smorgasbord
I am learning to solve multiplication problems using a variety of
mental strategies.
Work it out in your head
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.
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
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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
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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
8 X 8 = 64
So 4 X 16 = 64
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÷2
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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
1) 4 X 25 = ? 100, 2 X 50 = 100
answering each of these questions
will be displayed. Please note that
this is only one possible solution.
2) 3 X 27 = ? 81, 9 X 9 = 81
Your answer however should be the
same.
3) 6 X 39 = ?
234, (6 X 40) – (6 X 1 ) = 234
4) 7 X 22 = ?
154, (7 X 20) + (7 X 2) = 154
5) 4 X 24 = ?
96, (4 X 12 = 48) double this amount.
Need some more practise? Try Pg34 & 35 of Teacher Tools Multiplication
and Division Book Numeracy resources