Learning objective: To be able to use partitioning to double or halve numbers.

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# Place value - PowerPoint PPT Presentation

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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## PowerPoint Slideshow about 'Place value' - Audrey

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Presentation Transcript

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.
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
• 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

+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

Have a go at this calculation using your knowledge of partitioning and known halves.
• Q. What is half of 38?
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 )
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.
• 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)