Addition and Subtraction

AdditionRelate addition to combining two groups and counting

on and record in a number sentence using + and = signs.

13 + 24 = 37Record addition by: model and images

+

Your turn

• 23 + 26 =

When the children are comfortable with this we move onto adding on

a number line.13 + 24 = 37

13

+10 +10+1 +1 +1 +1

23 33 3734 3635

Your turn

• 32 + 25 =

From this we move onto using partitioning both numbers.

35 + 23

30 + 20 = 50

5 + 3 = 8

50 + 8 = 58

Your turn

43 + 56 =

Develop methods for adding two digit and three digit numbers by partitioning second number only.

246 + 37=246 + 30 = 276276 + 7 = 282

Your turn

• 145 + 54 =

Then we develop written methods for addition of two and three digit numbers using expanded methods of recording.

375 + 67

300 70 5+ 60 7

300 130 12 = 442

How can we apply this knowledge?

Problem solving

T= Target

I= Information

N= Number sentence

A=Answer

Mina and Ben play a game. Mina scores 70 points. Ben scores 42 points. How many points did they score in total?T= How many points did they score in

total?

I = 70 42 +

N= 70 + 42 =

A=

Your turnMina and Ben play a game. Mina scores 35 points. Ben scores 63 points. How many points did they score in total?

T=

I=

N=

A=

There are 265 children at Hill School. 102 children have a packed lunch. 27 children go home for lunch. The other children have a school lunch. How many children have

school lunch?

Subtraction

Relate subtraction to taking away by counting back and as counting on and record in a number sentence using the – and = signs.

Subtraction not crossing through the tens boundary.

46 – 25 =

- 25 = 21

In a subtraction calculation we always write the digits of the second number, we don’t draw the image!

Subtraction crossing the tens boundary.

53 – 27= - 27 = 26

Your turn

Have a go, using models and images at these two calculations.

1.) 57- 32 =

2.) 42 – 16 =

Once the children are comfortable with this strategy we move them

onto subtraction on a number line.

49 – 14 =

49 - 10

39

-1

38

-1

373635

-1 -1

Your turn

56 – 38 =

Subtraction by partitioning not crossing the tens boundary.

48 – 32 =

40 – 30 = 10

8 - 2 = 6

10 + 6 = 16

Subtraction crossing the tens boundary using partitioning.

53 – 37 =

50 – 30 = 20

3- 7= We can’ t do this so we take one of the above tens.

13 – 7 = 6

10 + 6 = 16

10

Partitioning only the second number.

78 – 43 =

78 – 40= 38

38 - 3= 35

This is the same process even when crossing through the tens barrier.

63 - 28 =

63 - 20 = 43

43 - 8= 35

Begin to record calculations in preparation for an efficient

standard method- expanded decomposition. 81

- 57 70 and 11

50 and 7

20 and 4

= 24

Problem Solving

Sita had 87p. She spent 35p.How much money did she have left?T= How much money did she have left?

I = 87p 35p left -

N= 87p – 35 p=

A=

There are 104 children at Delton School.48 children are girls. How many are boys?

T= How many are boys?

I= 104 48 -

N=104- 48

A=