Download Children will understand equal groups and share items out in play

Survey
yes no Was this document useful for you?
   Thank you for your participation!

* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project

Document related concepts

Location arithmetic wikipedia , lookup

Arithmetic wikipedia , lookup

Transcript
Children will understand equal groups and share items out in play and problem solving. They will count in 2s and 10s and later
in 5s. They will create number stories to show their understanding.
Children will develop their understanding of division and use jottings to support calculation
They will continue to learn tables - 2s, 5s, 10s, 3s and 4s.

Sharing equally
6 sweets shared between 2 people, how many do they each get?

Grouping or repeated subtraction
There are 6 sweets, how many people can have 2 sweets each?
They will create number stories to show their understanding.
Repeated subtraction using a number line or bead bar

12 ÷ 3 = 4
-3
0
1
2
-3
3
3
4
-3
5
6
7
-3
8
3
9
10 11 12
3
3
The bead bar will help children with interpreting division calculations such as 10 ‚ 5 as ‘how many 5s make 10?’

Using symbols to stand for unknown numbers to complete equations using inverse operations
÷2=4
20 ÷  = 4
÷=4
Ensure that the emphasis in Y3 is on grouping rather than sharing.Children will continue to use:

Repeated subtraction using an empty number line
24 ÷ 4 = 6
-4
0
-4
4
-4
8
-4
12
-4
16
-4
20
24
Children should also move onto calculations involving remainders.
13 ÷ 4 = 3 r 1
4
4
4
0 1
5
9
13

Using symbols to stand for unknown numbers to complete equations using inverse operations
26 ÷ 2 = 
24 ÷  = 12
 ÷ 10 = 8
Children will develop their use of repeated subtraction to be able to subtract multiples of the divisor. Initially, these
should be multiples of 10s, 5s, 4s, 3s, 2s and 1s – numbers with which the children are more familiar.
72 ÷ 5
-2
0
-5
2
-5
7
-5
12
17
-5
-5
22
-5
-5
-5
27 32 37
Moving onto:
-5
-5
-5
-5
42 47 52
-5
-5
57 62
-5
67
-5
72
-50
-5
-5
r2
_______________________________________________________
1
1
1
1
10
02
7
12
17
22
72
Stage 1: Mental division using partitioning
**Secure knowledge of multiplication facts will aid understanding of partitioning.
One way to work out TU ÷ U mentally is to partition TU into a multiple of the divisor plus the remaining ones, then divide
each part separately.
Informal recording in Year 4 for 84 ÷ 7 might be:
In this example, using knowledge of multiples, the 84 is partitioned into 70 (the highest multiple of 7 that is also a multiple
of 10 and less than 84) plus 14 and then each part is divided separately using the distributive law.
Stage 2: Short division of TU ÷ U
'Short' division of TU ÷ U can be introduced as a more compact recording of the mental
For 81 ÷ 3, the dividend of 81 is split into 60, the highest multiple of 3 that is also a multiple
method of partitioning.
10 and less than 81, to give 60 + 21.Each number is then divided by 3.

Short division of two-digit number can be introduced to children who are
confident with multiplication and division facts and with subtracting multiples of
10 mentally,and whose understanding of partitioning and place value is sound.
The short division method is recorded like this:
For most children this will be at the end of Year 4 or the
beginning of Year 5.
This is then shortened to:

The accompanying patter is 'How many threes divide into 80 so that the
answer is a multiple of 10?' This gives 20 threes or 60, with 20 remaining. We now
ask: 'What is
The carry digit '2' represents the 2 tens that have been exchanged for 20 ones. In the
first recording above it is written in front of the 1 to show that 21 is to be divided by 3. In
21divided by three?' which gives the answer 7.
second it is written as a superscript.
The 27 written above the line represents the answer: 20 + 7,or 2 tens and 7 ones.
Stage 3: Vertical Numberline
196
6x10
136
Stage 4: 'Expanded' method for TU ÷ U









This method is based on subtracting multiples of the divisor from the number to be divided,
the dividend.
For TU ÷ U there is a link to the mental method.
As you record the division,ask: 'How many nines in 90?' or 'What is 90 divided by 9?'
Once they understand and can apply the method, children should be able to move on from
TU ÷ U to HTU ÷ U quite quickly as the principles are the same.
This method, often referred to as 'chunking', is based on subtracting multiples of the divisor,
or 'chunks'. Initially children subtract several chunks, but with practice they should look for
the biggest multiples of the divisor that they can find to subtract.
Chunking is useful for reminding children of the link between division and repeated
subtraction.
However, children need to recognise that chunking is inefficient if too many subtractions have
to be carried out. Encourage them to reduce the number of steps and move them on quickly to
finding the largest possible multiples.
The key to the efficiency of chunking lies in the estimate that is made before the chunking
starts. Estimating for HTU ÷ U involves multiplying the divisor by multiples of 10 to find the two
multiples that 'trap' the HTU dividend.
Estimating has two purposes when doing a division:
o
to help to choose a starting point for the division;
o
to check the answer after the calculation.
Children who have a secure knowledge of multiplication facts and place value should be able to move
on quickly to the more efficient recording on the right.
Stage 3
97 ÷ 9
Any remainders should be shown as integers, i.e. 14 remainder 2 or 14 r 2.
Children need to be able to decide what to do after division and round up or down accordingly. They
should make sensible decisions about rounding up or down after division. For example 62 ÷ 8 is 7
remainder 6, but whether the answer should be rounded up to 8 or rounded down to 7 depends on
the context.
e.g. I have 62p. Sweets are 8p each. How many can I buy?
Answer: 7 (the remaining 6p is not enough to buy another sweet)
Apples are packed into boxes of 8. There are 62 apples. How many boxes are needed?
Answer: 8 (the remaining 6 apples still need to be placed into a box
Stage 5: Short division of HTU ÷ U
** secure knowledge of number facts is needed for this method to be used confidently
Children will continue to use written methods to solve short division TU ÷ U.
Children can start to subtract larger multiples of the divisor, e.g. 30x


'Short' division of HTU ÷ U can be introduced as an
alternative, more compact recording. No chunking is
involved since the links are to partitioning, not repeated
subtraction.
The accompanying pattern is 'How many threes in
For 291 ÷ 3, because 3 × 90 = 270 and 3 × 100 = 300, we
use 270 and split the dividend of 291 into 270 + 21. Each
part is then divided by 3.


290?' (the answer must be a multiple of 10). This gives
90 threes or 270, with 20 remaining. We now ask: 'How
many threes in 21?' which has the answer 7.
Short division of a three-digit number can be
introduced to children who are confident with
multiplication and division facts and with subtracting
multiples of 10 mentally, and whose understanding of
partitioning and place value is sound.
For most children this will be at the end of Year 5 or
the beginning of Year 6.
The short division method is recorded like this:
This is then shortened to:
The carry digit '2' represents the 2 tens that have been
exchanged for 20 ones. In the first recording above it is
written in front of the 1 to show that a total of 21 ones
are to be divided by 3.
The 97 written above the line represents the answer:
90 + 7,or 9 tens and 7 ones.
196 ÷ 6
32 r 4
6 ) 196
- 180
30x
16
12
2x
4
Answer :
32 remainder 4 or
32 r 4
Any remainders should be shown as integers, i.e. 14 remainder 2 or 14 r 2.
Children need to be able to decide what to do after division and round up or down accordingly. They should make sensible
decisions about rounding up or down after division. For example 240 ÷ 52 is 4 remainder 32, but whether the answer should
be rounded up to 5 or rounded down to 4 depends on the context.
972 ÷ 36
27
36 ) 972
- 720
20x
252
- 252
7x
0
Answer :
27
Any remainders should be shown as fractions, i.e. if the children were dividing 32 by 10, the answer should be shown as 3
2
/10 which could then be written as 3 1/5 in it’s lowest terms.
Stage 6: Long division
The next step is to tackle HTU ÷ TU, which for most children
will be in Year 6.
The layout on the right, which links to chunking, is in essence
How many packs of 24 can we make from 560 biscuits?
Start by multiplying 24 by multiples of 10 to get an
estimate. As 24 × 20 = 480 and 24 × 30 = 720, we know
the 'long division' method. Recording the build-up to the
quotient on the left of the calculation keeps the links with
'chunking' and reduces the errors that tend to occur with the
positioning of the first digit of the quotient.
Conventionally the 20, or 2 tens, and the 3 ones forming the
answer are recorded above the line, as in the second
recording.
the answer lies between 20 and 30 packs. We start by
subtracting 480 from 560.
In effect, the recording above is the long division method,
though conventionally the digits of the answer are
recorded above the line as shown below.
Extend to decimals with up to two decimal places. Children should know that decimal points line up under each other.
87.5 ÷ 7=
12.5
7 ) 87.5
- 70.0
10x
17.5
- 14.0
2x
3.5
- 3.5
0.5x
0
Answer :
12.5
+ - + - + - + - + - + - +
By the end of year 6, children will have a range of calculation methods, mental and written. Selection will depend
upon the numbers involved.
Children should not be made to go onto the next stage if:
1) they are not ready.
2) they are not confident.
Children should be encouraged to approximate their answers before calculating.
Children should be encouraged to check their answers after calculation using an appropriate strategy.
Children should be encouraged to consider if a mental calculation would be appropriate before using written methods.