Halving

Success Criteria

L.I. To use halving as a strategy for mental multiplication and division.

• I can halve numbers by dividing them by 2.

• I can use partitioning to halve larger numbers.

• I can create and continue halving sequences.

How would you double 63?

You could partition the number into tens and ones.

63 = 60 and 3

Double 60 = 120

Double 3 = 6

Finally, recombine the numbers.

120 + 6 = 126

Let’s recap: Doubling

Now please double: How would you double 82?

You could partition the number into tens and ones.

82 = 80 and 2

Double 80 = 160

Double 2 = 4

Finally, recombine the numbers.

160 + 4 = 164

ANSWERS: How would you double 82?

You could partition the number into tens and ones.

82 = 80 and 2

Double 80 = 160

Double 2 = 4

Finally, recombine the numbers.

160 + 4 = 164

Now, onto: Halving

To halve something, we divide it by two (÷ 2).

What is the number sentence for this calculation?

4m ÷ 2 = 2m

This is easy, but what if the numbers are larger?

Can halving help us then?

This snake is half as long.

This snake is 4m long.

Halving How would you halve 66?

Partition the number into tens and ones.

66 = 60 and 6

Half of 60 or 60 ÷ 2 = 30

Half of 6 or 6 ÷ 2 = 3

Finally, recombine the numbers.

30 + 3 = 33

Halving How would you halve 66?

Partition the number into tens and ones.

66 = 60 and 6

Half of 60 or 60 ÷ 2 = 30

Half of 6 or 6 ÷ 2 = 3

Finally, recombine the numbers.

30 + 3 = 33

Halving by Partitioning Now try halving these numbers by partitioning them.

Challenge 1 Challenge 2 Challenge 3

1. 28 = 2. 64 = 3. 86 =

1. 124 = 2. 86 = 3. 240 =

1. 264 = 2. 324 = 3. 740 =

Make sure you show your working out.

Halving by Partitioning Now try halving these numbers by partitioning them.

Challenge 1 Challenge 2 Challenge 3

1. 28 = 2. 64 = 3. 86 =

1. 124 = 2. 88 = 3. 240 =

1. 264 = 2. 328 = 3. 740 =

14 32 43

62 44 120

132 164 370

Did you get them right?

If not, can you work out where you went wrong?

Please only do the halving activity

In a Minute Consider the following questions and discuss them with someone in

your family:

You have exactly one minute to tell somebody in your home:

• What, if any, have you found most difficult out of doubling and halving?

• Why do you think this is?

• What could you do to make you feel more confident in this area?