Transcript Partitioning and doubling

Learning objective:
To be able to use
partitioning to double or
halve numbers.
Place value

Numbers are categorised as being either
units/ones, tens, hundreds or thousands etc.

The position of the digit within an number
shows its value according to its ‘place’.

In whole numbers the number on the far right
is always the units/ones column, next on the
left comes the tens, then the thousands etc.
Th H T U
Partitioning

Partitioning is the breaking down of a number into
several components according to its place value.

E.g. 485 = 400 + 80 + 5

The zeros represent a place holder of the other digits (
e.g. tens and units) and without them the number would
simply look like a single unit of 4.
..\..\..\..\Desktop\Maths ITP\placevalue_pc.EXE
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Partitioning and doubling
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Why do we need to partition when
doubling?
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By partitioning a number we can use
known doubles of smaller numbers and
then add these together to calculate the
answer.

E.g. double 47 is not a double that most
people know of by heart.

BUT of you partition it into tens and units
( 40 + 7)

Double 40 is relatively easy = 40x 2 = 80
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Double 7 is a known double = 7 x 2 = 14
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Add these together  80
+14
94
Have a go at this calculation using
your knowledge of partitioning and
known doubles.
Q. What is double 67?
Partitioning and halving

Why do we need to partition when
halving?
By partitioning a number we can use
known halves of smaller numbers and
then add these together to calculate
the answer.
 E.g. half of 58???????????

Partition 58 into tens and units
(50 + 8)
 Half of 50 = 25 ( ½ or divide by 2)
 Half of 8 = 4
 Add these together  25
+ 4
29

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Have a go at this calculation using your
knowledge of partitioning and known
halves.

Q. What is half of 38?
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Remember  if the number you are halving is
an even number it will always halve exactly.

Whereas if the number is an odd number the
answer will always have the fraction of a half
in it ( e.g. half of 13 = 6 ½ )

The easiest way to halve odd numbers is to
half the even number just before it and then
add on a half to that number (e.g. 13  half
of 12 is 6 + ½ = 6 ½ )
Well done you can now
partition numbers to
find doubles and halves!
☺
Main activity:

With your partner, roll 2 dice to find 2-digit numbers. Then
partition them into tens/units and find the doubles/halves and
record in your exercise books.
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E.g. 34  30 + 4
30 = 60 = 15
4=8=2
Therefore 34 = 68 (60 + 8) = 17 (15 + 2)
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Please remember to write the long date along with the title. LO:
To be able to use partitioning to double or halve numbers.
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Year 3’s to work on numbers between 1-50 first (x 10) then go
onto numbers 50-100. ( x 5)
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Year 4’s to work on numbers between 1-100. (x 10)
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Extension: roll dice 3 times to create 3-digit numbers and find
doubles/halves by partitioning into hundreds/tens/units (x 5)