Transcript Addition in Key Stage 2

How to Help Your Child with
Maths
INSPIRE 5KW
This morning?
“They do it all differently these days!”
Bridging the gap
They are teaching you this morning!
What is important?
• A strong foundation in the basics
– Just like the foundations of a house, if the
basics aren’t solid then cracks will appear
– So, keep returning to the fundamentals
– Your child should not just be familiar with
the basics, but fluent
– Don’t be afraid to do the old drills and
skills
Anything else important?
• Multiplication tables
• Rapid and accurate addition and subtraction
• Telling the time, analogue and digital
• Drip, drip, drip….
Anything else important?
• A sound understanding of place value is
very important
Not millions Th H T U . 1/10 1/100
So what are the basics?
•
•
•
•
•
Addition
Subtraction
Multiplication
Division
Problem solving
Some practical ideas…
Times tables in the car…drill and quickfire
Make it real:
Do I have enough money?
What change should I get?
Which is the best value?
What time will it be in 25 minutes?
If we leave now will we catch the train, bus, cinema…
Cooking, weighing, measuring.
Do I have enough rice to make this dish?
What methods do we use?
Mental first!
• To equip children for real life their mental maths
skills are the most important.
• Speeding up the accuracy and fluency of mental
methods will help with written methods later.
What methods do we use?
Mental strategies
• Bonds to 10 and 100
• Partitioning.
24 + 43 =
20 + 40 = 60
4+ 3= 7
60 + 7 = 67
What methods do we use?
Your turn….
• Play I say, you say with your bonds to 10, then 100.
then….
• Solve this calculation by partitioning…
• 54 + 32 =
• If you finish early, you can practice by using the
number cards on your desks, turn over 2.
What methods do we use?
• Written methods
– Using a variety of methods
– Building towards a standard method
– They often follow the path from an
expanded method
to a shorter method
and finally a compact method
Addition in Key Stage 2
The three different written forms are:
• Expanded Method
75
+23
98
70 + 5
+ 20 + 3
90 + 8
Addition in Key Stage 2
Shorter Method
75
+23
8
90
98
Addition in Key Stage 2
• The Compact Method
75
+23
98
Addition in Key Stage 2
• Carrying as part of the Compact
Method
78
+23
101
1
Notice the carry written
under the line
Addition in Key Stage 2
Your turn….
Solve this calculation
65
+ 78
and this one
145
227
Addition in Key Stage 2
• Decimals
“Decimals Don’t Dance!”
• The decimal point stays in the same place
71.3
2.25

71.3
2.25 
Decimals should not be written in the square
of a book as they have no place value. They
should be written on a line 1 2.4
Addition in Key Stage 2
Your turn….
Line up the decimals to solve this
calculation using the compact method
43.2 + 12.25 =
Subtraction in Key Stage 2
• Expanded method
78
-23
55
70 + 8
- 20 + 3
50 + 5
Subtraction in Key Stage 2
• Shorter method
78
-23
5
50
55
Subtraction in Key Stage 2
• Compact method
78
-23
55
Subtraction in Key Stage 2
• Common problems
83
-48
Children will often say 3 - 8 = 5
so ask them to do a concrete check:
‘I have 3 pieces of fruit. Can you take
away 8 of them?’
Subtraction in Key Stage 2
Common problems
We talk about numbers and digits to make
things clearer
So 56 is the number…
…but 5 and 6 are the digits
So when writing down a subtraction, always
put the bigger number on the top
Subtraction in Key Stage 2
Exchanging
• We don’t ‘borrow’ because we are never going to pay
anything back
73
-28
76313 Having exchanged, start the sum again:
-2 8
13 - 8 we can do = 5
4 5 ‘6 tens - 2 tens is how many tens?’
rather than 60 - 20 as children
will write 40 5
By years 5 and 6 we expect children to select the best
method, so for 1002 - 998 a vertical method is NOT best
Subtraction in Key Stage 2
Your turn!
Choose the best method to solve these
subtraction problems – you may be able to
work out the answer in your head.
a) 123 - 99 =
b) 243 – 39 =
c) 386 – 293 =
Preparing for Multiplication
• Children must know their tables - fluently
• ? X 5 = 15
• 3 x ? = 15
• 3x5=?
• Mad Minutes….your turn!
Preparing for Multiplication
• Place value
Th
H
T U 1/10 1/100
• Multiplying by 10
Move each digit one place to
L
the left (remember Multip ication)
H T U That leaves
1 7 a space in
1 7
to which we
put a zero to hold the place
Preparing for Multiplication
• Common Errors
– Why don’t we say ‘add a zero’ when
multiplying by 10?
• 1.7 x 10 = 1.70 we have added a zero but
have not made any difference to the number
– Why do we need a zero at all?
• This is 170 without a zero
H T U
which looks like
1 7
17
Preparing for Multiplication
• Your turn:
Use your white boards to multiply these
numbers by 10
36 x 10 =
23 x 10 =
37 x 10 =
H T U
Multiplication in KS2
• Grid Method
19 x 6
10
6 60
9
54
60
+ 54
114
Multiplication in KS2
• Grid Method
29 x 6
20
6 120
9
Knowing 2 x 6 = 12 is a basic fact
So
20 x 6 = 120 can be ‘grown’ from this
basic fact
Multiplication in KS2
• Grid Method
47 x 6
6
How would you
partition 47?
Multiplication in KS2
• Grid Method
27 x 23
20
400
140
20
7
2x2=4
20x2=40
20 x20 = 400
3
60
21
400
140
+ 60
21
621
Multiplication in KS2
Grid method
Your turn….
22 x 14 =
Multiplication in KS2
• Shorter Vertical Method
19
x 6
60
54
114
write this first
(10 x 6)
(9 x 6)
They do this method in year 6, after they have a
confident grasp of the grid method.
Division in KS2
• Tables! Tables! Tables!
• How to rally robin
Your turn: try it with 2, 5 and 10 x tables.
Stand up bingo
Write any 5 of the following numbers on your
boards.
0, 2, 4, 5, 6, 8, 10, 12, 14, 15,
20, 22, 24, 26, 28, 30
Thank you for coming!
• This presentation is available on our
classblog… as is a more comprehensive
version.
• Please come to see us with any questions