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Year 5 Term 2 Unit 9 Day 1

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L.O.1 To be able to add and subtract any pair of two-digit numbers

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30+40 Write the answer in your books.

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Q. How did you work that out? We can get the answer using: the number fact and then applying place value x 10 We can use a similar method for subtraction LOOK…. 50 – 20 The number fact is 5 – 2 And the place value is x 10

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Try these using the same method where possible: 80 – – –

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In your book write synonyms for: +-

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L.O.2 To be able to add or subtract the nearest multiple of 10,100 or 1000 then adjust.

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Round these numbers: 1. To the nearest To the nearest To the nearest Write in your books how much we had to adjust each number by.

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We can use rounding as a strategy for addition and subtraction. 93 – 69 Thus: 1.What multiple of 10 is nearest to 69? 2.What is 93 – 70? 3.Have we subtracted more or less than 69? 4.How should we adjust the answer to make it correct?

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Our sum is: 93 – 69= ( 93 – 70 ) + 1 = = 24 This can be shown on a number line

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Our sum is now: 93 – 69= ( 93 – 70 ) + 1 = = 24 This can be shown on a number line

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We are going to try this: = ( ) + 1 = = 419 Draw the number line in your books

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Try this: 286 – 97 = (286 – 100) + 3 = = 189 We need a volunteer to draw the number line!

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Try this: 5250 – 1998 = (5250 – 2000) + 2 = = 3252 We need a volunteer to draw the number line

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Try this = ( ) – 1 = 658 – 1 = 657 We need a volunteer to draw the number line

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Do these : include the written sum and the number line. All groups: + Spheres + Prisms 289 – – – –

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Look at these: – – – – 71 Q.For which of these would you use the rounding and adjusting strategy? Q. How would you tackle the other questions?

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By the end of the lesson the children should be able to: For example, work out mentally that: = 370 as – 4 = 374 – 4 = 370 and 4005 – 1997 = 2008 as 4005 –

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Year 5 Term 2 Unit 9 Day 2

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L.O.1 To be able to recall addition and subtraction facts for each number to 20 and extending to multiples of 10.

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Write the answer in your books to the following: 15 – – 5 12 – – – 10

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Q. What strategies can we use for quick recall? We can : 1. double and subtract or add e.g = round up or down and subtract or add the difference e.g = Subtract even numbers by halving it and subtracting it twice e.g.16 – 4 = 16 – 2 - 2

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We can use the same strategies with multiples of 10. Do these in your book: – – 100 Can you see the similarities?

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Q. Did you see the similarities? Q. What strategies did you use?

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L.O.2 To be able to add several numbers.

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Copy these numbers into your book as they are here and calculate the total. Q. How did you find the total?

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To find the total we can; 1.look for numbers that sum start with the largest number first

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Now try these: Q. What strategies did you use?

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Look at this calculation: Q. What strategies do you use?

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To find the total we can; 1.look for unit pairs that make start with the largest number first

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Copy these numbers into your book and add them up. Remember to use pairing strategy.

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The answer is 50.

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Q. How many pairs of numbers sum to 10? = 5 X 10

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Look at this calculation: Q. What multiplication is this equivalent to?

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To find the answer we must first do the calculation using our addition strategies = is the equivalent to 4 X 4 Q Who got this right?

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Q. How can we represent the following as a multiplication?

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To find the answer we must first do the calculation using our addition strategies When we look at the numbers we can see that 18 and 22 make 40 ; a multiple of is also a multiple of 20 That means that there are 3 multiples of 20 so 60 is the equivalent to 20 X 3

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Lets look at this one Q. What strategies could we use to find the sum?

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To find the total we can; 1.look for numbers that sum start with the largest number first look for multiples look for unit pairs of

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Showing your method, do the following in your books:

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Q. What strategies did you use to find the answers? Q. Which strategy do you think is best for this calculation?

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Copy this into your books

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In your books write down sets of numbers from the table that you can total using all the addition strategies we have looked at today.

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Year 5 Term 2 Unit 9 Day 3

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L.O.1 To be able to add near doubles including decimals.

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Look at this calculation Q What strategy could you use to find the sum? Look at the numbers, they are near doubles of each other.

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To calculate the sum we simply have to double one of the numbers and adjust the answer. E.g = (35 x 2) = 71 OR = (36 x 2) – 1 = 71

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Try these using one or all of the near doubling strategies: = = = =

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Now work out these calculations and Q. How did you work them out?

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To find the sum of we double and adjust the numbers. 16 x 2 = = 33 If 16 is the same as 1.6 x 10 and 17 is the same as 1.7 Q. How can this help us work out ?

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The answer is simple. If = 33 then = 3.3 We have divided 33 by 10 OR moved the decimal point one place to the left.

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In your books work out the following using the same method TiP : do the whole numbers first

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The answers are:

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L.O.2 To be able to add several numbers using a variety of strategies for mental addition. To solve mathematical problems or puzzles, recognise and explain patterns and relationships.

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Look at this table

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What is the total for this column and this row?

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What do you notice about the totals?

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Yes. They all add up to 42!!

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Are there any other patterns?

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Look at these numbers

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This known as a 3 x 3 magic square

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Q What do you think would happen if we subtract 7 from each number? Would it still be a magic square?

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Lets check. What is the magic total for the square now?

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Yes. It is 21.How could we have predicted this happening?

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Would the square still be magic if we aded or subtracted ANY number from each square?

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It would have to be the same number from each square

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Lets look at the number patterns with some different numbers.

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Q What do you notice about the answers we have found each square that we have tried?

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Each answer we have had has been a multiple of 3!

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The total we found (42) is 14 X

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Remember when we subtracted 7 from each number? The total (21) is 3 x 7…MAGIC

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What is the sum of the first row and column?

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It is 46. Is this a multiple of 4?

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No. It isnt

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Do all the rows and columns total 46?

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Yes they do. Can you find any sets of 4 numbers that total 46?

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Lets have a look at some

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This is made up of 4 magic squares put together

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Do these numbers add up to 46?

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Q Will every diagonal of 4 total 46? On your on sheet highlight 4 diagonals and test.

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Lets look at some of your answers

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L.O.2 To be able to add several numbers using a variety of strategies for mental addition. To solve mathematical problems or puzzles, recognise and explain patterns and relationships.

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