Year 5 Term 2 Unit 9

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# Year 5 Term 2 Unit 9 - PowerPoint PPT Presentation

Year 5 Term 2 Unit 9. Day 1. L.O.1 To be able to add and subtract any pair of two-digit numbers. 30+40 Write the answer in your books. Q. How did you work that out? We can get the answer using: the number fact 3 + 4 and then applying place value x 10

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L.O.1

To be able to add and subtract any pair of two-digit numbers

30+40

Q. How did you work that out?

We can get the answer using:

the number fact 3 + 4

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

Try these using the same method where possible:

80 – 50

70 + 40

34 + 54

75 – 40

46 + 52

58 – 25

80+ 40

L.O.2

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

Round these numbers:

1. To the nearest 10

34277866 55

2. To the nearest 100

16776135485521

3. To the nearest 1000

243573284982 6525 7721

93 – 69

Thus:

• What multiple of 10 is nearest to 69?
• What is 93 – 70?
• Have we subtracted more or less than 69?
Our sum is:

93 – 69 = ( 93 – 70 ) + 1

= 23 + 1

= 24

This can be shown on a number line.

+1 -70

23 24 93

Our sum is now:

93 – 69 = ( 93 – 70 ) + 1

= 23 + 1

= 24

This can be shown on a number line.

-70

+ 1

23 24 93

We are going to try this: 368 + 51.

368 + 51 = (368 + 50) + 1

= 418 + 1

= 419

Draw the number line in your books.

+50 +1

368 418 419

Try this:

286 – 97 = (286 – 100) + 3

= 186 + 3

= 189

We need a volunteer to draw the number line!

Try this:

5250 – 1998 = (5250 – 2000) + 2

= 3250 + 2

= 3252

We need a volunteer to draw the number line

Try this

458 + 199 = (458 + 200) – 1

= 658 – 1

= 657

We need a volunteer to draw the number line

Do these :

include the written sum and the number line.

All groups: + Spheres + Prisms

289 – 98756 – 1972348 – 1996

645 + 69 572 + 1965932 + 2995

584 – 97 615 - 498 3688 - 1994

1267 + 88 1546 + 9975482 + 1988

Look at these:

73 + 26182 – 95

6003 – 599456 – 29

73 + 200 583 – 71

• For which of these would you use the rounding and adjusting strategy?

Q . How would you tackle the other questions?

By the end of the lesson the children should be able to:

For example, work out mentally that:

274 + 96 = 370

as 274 + 100 – 4 = 374 – 4

= 370

and 4005 – 1997 = 2008

as 4005 – 2000 + 3

L.O.1

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

15 – 712 + 89 + 8 3 + 4

7 + 611 + 1114 – 5

12 – 46 + 138 – 517 + 6

19 – 10

Q. What strategies can we use for quick recall?

We can :

1. double and subtract or add

e.g. 6 + 7 = 6 + 6 +1

2. round up or down and subtract or add the difference

e.g. 8 + 12 = 8 + 10 + 2

• Subtract even numbers by halving it and subtracting it twice

e.g. 16 – 4 = 16 – 2 - 2

We can use the same strategies with multiples of 10.

70 + 6010 +20140 – 50190 – 100

Can you see the similarities?

Q. Did you see the similarities?

Q. What strategies did you use?

L.O.2

To be able to add several numbers.

40 + 90 + 60 + 50

Copy these numbers into your book as they are here and calculate the total.

Q. How did you find the total?

To find the total we can;

1. look for numbers that sum 100

60 + 40

90 + 60 +

Now try these:

60 + 70 + 20 + 80 + 20 + 30 + 80 + 70

50 + 60 + 30 + 80 + 40 + 90 + 40 + 50

Q. What strategies did you use?

Look at this calculation:

63 + 15 + 35

Q. What strategies do you use?

To find the total we can;

1. look for unit pairs that make 10

35 + 15

63 + 35

1 + 2 + 3 + 4 + 5 + 5+ 6 + 7 + 8 + 9

Remember to use pairing strategy.

Q. How many pairs of numbers sum to 10?

1 + 2 + 3 + 4 + 5 + 5+ 6 + 7 + 8 + 9

= 5 X 10

Look at this calculation:

4 + 4 + 3 + 5

Q. What multiplication is this equivalent to?

To find the answer we must first do the calculation using our addition strategies.

4 + 4 + 3 + 5 = 16

16 is the equivalent to 4 X 4

Q Who got this right?

To find the answer we must first do the calculation using our addition strategies.

18 + 20 + 22

When we look at the numbers we can see that

18 and 22 make 40 ; a multiple of 20

20 is also a multiple of 20

That means that there are 3 multiples of 20 so 60 is the equivalent to 20 X 3

Let’s look at this one

48 + 49 + 50 + 51 + 52

Q. What strategies could we use to find the sum?

To find the total we can;

1. look for numbers that sum 100

48 +52

52 + 51 +

3. look for multiples

50

4. look for unit pairs of 10

51 + 49

18 + 19 + 20 + 21 + 22

26 + 28 + 30 + 32 + 34

64 + 66 + 70 + 74 + 76

83 + 85 + 90 + 97 + 95

Q. What strategies did you use to find the answers?

Q. Which strategy do you think is best for this calculation?

18 + 19 + 20 + 21 + 22

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.
L.O.1

To be able to add near doubles including decimals.

Look at this calculation

35 + 36

Q What strategy could you use to find the sum?

Look at the numbers, they are near doubles of each other.

To calculate the sum we simply have to double one of the numbers and adjust the answer.

E.g. 35 + 36 = (35 x 2) +1

70 + 1 = 71

OR

35 + 36 = (36 x 2) -1

72 – 1 = 71

Now work out these calculations

17 + 16 and 1.7 + 1.6

Q. How did you work them out?

16 x 2 = 32

32 + 1 = 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 1.6 + 1.7?

If 16 +17 = 33

then 1.6 + 1.7 = 3.3

We have divided 33 by 10

OR

moved the decimal point one place to the left.

In your books work out the following using the same method

12 + 13 1.2 + 1.3

25 + 24 2.5 +2.4

44 + 43 4.4 + 4.3

TiP : do the whole numbers first

25 2.5

49 4.9

87 8.7

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.

Would it still be a magic square?

Q Will every diagonal of 4 total 46?

On your on sheet highlight 4 diagonals and test.

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.