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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’.

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Learning objective:

To be able to use partitioning to double or halve numbers.


Place value
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.



Partitioning
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


Partitioning and doubling
Partitioning and doubling

  • Why do we need to partition when doubling?

  • 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

Double 7 is a known double = 7 x 2 = 14

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
Partitioning and halving partitioning and known doubles.

  • 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???????????




  • Remember partitioning and known halves. 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 )



Main activity: halves!

  • 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.

  • E.g. 34  30 + 4

  • 30 = 60 = 15

  • 4 = 8 = 2

  • Therefore 34 = 68 (60 + 8) = 17 (15 + 2)

  • Please remember to write the long date along with the title. LO: To be able to use partitioning to double or halve numbers.

  • Year 3’s to work on numbers between 1-50 first (x 10) then go onto numbers 50-100. ( x 5)

  • Year 4’s to work on numbers between 1-100. (x 10)

  • Extension: roll dice 3 times to create 3-digit numbers and find doubles/halves by partitioning into hundreds/tens/units (x 5)


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