Transcript Parents` Workshop - Addition and Subtraction

Beaconside Parents’
Maths Workshop –
Addition and
Subtraction
5th March 2013
‘I didn’t learn to do
it that way!’
Maths! What’s your
experience?
• What are your first
thoughts?
• Do you panic?
• Have you any negative
experiences?
A world without numbers!
Be positive about number!
Children learn + and - by:
• Being confident about number – seeing that numbers are
everywhere.
• Using and experiencing a range of resources.
• Using and experiencing a range of methods so that they can
decide which is the best method to use:
Pictures; mental calculation - with or without jottings; structured
recording; calculator
How ?
• Understanding and using a selection of mental strategies
• Knowing number bonds ( ie 7+3=10, 18+2= 20)
• Place value ( understanding the order and the value of digits
including zero as the place holder)
• Money ( everyday money- calculating change)
• Problem solving
Resources
• Number line
• Counters
• Online games
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•
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Place value cards
Unifix sticks
Number square
Subitising activities
Subitising
• Subitising is the ability to recognise dot arrangements in
different patterns without counting.
• It is a fundamental skill in the development of number
sense and will help in the ability to add and subtract as well
as recall number bonds quickly.
We can learn:
there are 5 dots.
5 is more than 4
5 objects can be separated in to a set of 2 and 3
5 counters, no matter how arranged, still retain the same
numerical quantity
• The oral name for a set of 5 things is ‘five’
•
•
•
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Subitising: Activity 1
Play – show me (digits and numbers)
Fantastic for fast recall of number
bonds – support with + and – facts
without the need for counting.
Place Value – Activity 2
• We use place value cards in combination with
unifix cubes and 100 squares to recognise values
of numbers.
i.e. Use the place value cards to make the number
245
Partition the number.
Children understand 245 =
200+40+5 =245
Zero is important- it is the place
Holder and keeps the number in the
Correct column.
Activity 3 –addition with
jottings using partitioning
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

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
25 + 33= 58
Success Criteria:
Step 1: partition numbers ( tens 20 + 30) (units 5+3)
Step 2: add up the Tens ( 20 + 30 = 50)
Step 3: add up the Units ( 5+ 3 = 8)
Step 4: add both
(50 + 8= 58)
 55 + 26 ( 50 + 20= 70) ( 5+6= 11)
 70 + 11 = 81
 Key skills – adding 10s mentally – can you use a number
square to spot patterns when adding multiples of 10
to any number?
Activity 4: Back to number
bonds:
•
•
•
•
•
1+9 = 10 and 9+1=10
10+90 = 100 and 90+10 = 100
100+900 = 1000 and 900+100=1000
0.1 +0.9 = 1 and 0.9+0.1 = 1
Look for the patterns. Let the children discuss.
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Now have a go! Show me!
See the relationship between subtraction and addition
10–9 = 1
10-1 = 9
Now have a go! Show me!
Activity 5 – Number squares
- spot the patterns.
Number lines are an important
tool for addition and subtraction
Addition = count on
Subtraction is count back
Subtraction = difference
Addition = more than
Subtraction = less than
NUMBER LINES:
They show the order of numbers from left to right.
They are used to count on and back in 1s (Nursery+)
Counts on and back in 1s, 2s, 5s, 10s (Reception and
Year 1+)
• Count on and back in 100s (Year 2/Year 3+)
• Count on and back in 1000s(Year 4+)
• Count on and back in decimals/fractions (Year 5+)
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Number lines in action:
Addition
Always start with the ‘big’ number and count on.
8 + 5 = 13
+1 +1 +1 +1 +1
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
Activity 6 - Have a go…
Empty Number lines
(Addition):
Children will begin to use their knowledge
of partitioning and counting on in larger
steps as they become more confident.
34 + 23 = 57
+10
+10
+3
34

37
47
57
Followed by adding the tens in one jump and the units in one jump.
34 + 23 = 57
+20
34
+3
54
Have a go with a partner.
57
Number lines
(Subtraction):
Starting in Reception/Year 1
They use number lines by counting back
from the start number.
6–3=3
-1
-1
-1
___________________________________
0
1 2 3 4 5 6 7 8 9 10
The number line should also be used to show that 6 3 means the ‘difference between 6 and 3’ or ‘the
difference between 3 and 6’ and how many jumps
they are apart.
Empty Number lines
(Subtraction): Counting back
• From Year 2
Subtracting the tens in one jump and the units in one jump.

47 – 23 = 24
-20
-3
24 27

47
Bridging through ten can help children become more efficient.
42 – 25 = 17
-3
17
Have a go!
20
-2
22
-20
42
Empty Number lines
(Subtraction):
• ‘Finding the difference method’ – Counting on (Y2 –
Y6)
Success criteria
Put the smallest number on the left
Put the largest number on the right
Subtract by finding the difference and counting on in steps you feel
comfortable.
• Example:
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•
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82 – 47 = 35
Count up from 47 to 82 in jumps of 10 and jumps of 1.
+1 +1 +1
0
47 48 49 50
+10
60
+10
70
+10
+1 +1
80 81 82
Have a go!
Now on to the formal
methods…
• Addition: Year 4 onwards:
Children will begin to carry below the line. They will understand the value of the digits.
625
+ 48
673
1
7648
+ 1486
9134
1 11
783
+ 42
825
1
6584
+ 5848
12432
1 11
367
+ 85
452
11
4.2
64.32
786
3
+ 46.81
904.33
221
Working towards Formal Method –
Subtraction (End of Year 3)
Partitioning and decomposition
89
- 57
=
80
50
30
+
+
+
9
7
2
= 32
Initially, the children will be taught using examples that do not need the children to
exchange.
From this the children will begin to exchange.
71
- 46
=
=
Step 1
70
- 40
+
+
1
6
Step 2
60
- 40
20
+
+
+
11
6
5
The calculation should be
read as e.g. take 6 from 1.
=
25
This would be recorded by the children as
60
70
- 40
20
+
+
+
1
1
6
5
= 25
Leading to Formal method:
Year 4 onwards:
Children will be encouraged to use the formal decomposition method although they may
prefer to continue with the use of number lines.
Decomposition
754 – 86 =
614 1
//
754
- 86
668
Remember:
Be positive about maths!
• Children have a choice – allow them
to play with numbers and choose
their own methods.
• Support and share – let them
discuss!
• Maths can be practical – Food,
cooking, coins and money, measuring.
• Online games and resources can help.
Online games
Children love games to engage their learning. Try some of these:
Thank you all for
being positive
about maths!