4Q. How did you work that out? We can get the answer using:the number factand then applying place value x 10We can use a similar method for subtractionLOOK….50 – 20The number fact is 5 – 2And the place value is x 10
5Try these using the same method where possible: 80 – 5075 – 4058 – 2580+ 40
7L.O.2To be able to add or subtract the nearest multiple of 10 ,100 or 1000 then adjust.
8Round these numbers: 1. To the nearest 10 34 27 78 66 55 2. To the nearest 1003. To the nearest 1000Write in your books how much we had to adjust each number by.
9We can use rounding as a strategy for addition and subtraction. 93 – 69Thus:What multiple of 10 is nearest to 69?What is 93 – 70?Have we subtracted more or less than 69?How should we adjust the answer to make it correct?
10This can be shown on a number line. Our sum is:93 – 69 = ( 93 – 70 ) + 1== 24This can be shown on a number line.
11This can be shown on a number line. Our sum is now:93 – 69 = ( 93 – 70 ) + 1== 24This can be shown on a number line.-70+ 1
12We are going to try this: 368 + 51. 368 + 51 = (368 + 50) + 1 = ( ) + 1== 419Draw the number line in your books.
13Try this:286 – 97 = (286 – 100) + 3== 189We need a volunteer to draw the number line!
14Try this:5250 – 1998 = (5250 – 2000) + 2== 3252We need a volunteer to draw the number line
15Try this= ( ) – 1= 658 – 1= 657We need a volunteer to draw the number line
16include the written sum and the number line. Do these :include the written sum and the number line.All groups: Spheres Prisms289 – – – 1996584 –
17Look at these:– 956003 – – 29– 71For which of these would you use the rounding and adjusting strategy?Q . How would you tackle the other questions?
18By the end of the lesson the children should be able to: For example, work out mentally that:= 370as – 4 = 374 – 4= 370and 4005 – 1997 = 2008as 4005 –
20L.O.1To be able to recall addition and subtraction facts for each number to 20 and extending to multiples of 10.
21Write the answer in your books to the following: 15 –– 512 – –19 – 10
22Q. What strategies can we use for quick recall? We can :1. double and subtract or adde.g =2. round up or down and subtract or add the differencee.g =Subtract even numbers by halving it and subtracting it twicee.g. 16 – 4 = 16 – 2 - 2
23We can use the same strategies with multiples of 10. Do these in your book:– – 100Can you see the similarities?
24Q. Did you see the similarities? Q. What strategies did you use?
33Q. How many pairs of numbers sum to 10? = 5 X 10
34Look at this calculation: 4 + 4 + 3 + 5 Q. What multiplication is this equivalent to?
35To find the answer we must first do the calculation using our addition strategies. = 1616 is the equivalent to 4 X 4Q Who got this right?
36Q. How can we represent the following as a multiplication?
37To find the answer we must first do the calculation using our addition strategies. When we look at the numbers we can see that18 and 22 make 40 ; a multiple of 2020 is also a multiple of 20That means that there are 3 multiples of 20 so 60 is the equivalent to 20 X 3
38Let’s look at this one 48 + 49 + 50 + 51 + 52 Q. What strategies could we use to find the sum?
39To find the total we can; 1. look for numbers that sum 10048 +522. start with the largest number first3. look for multiples504. look for unit pairs of 10
40Showing your method, do the following in your books:
41Q. What strategies did you use to find the answers? Q. Which strategy do you think is best for this calculation?
42Copy this into your books 202492386176450603821740166242
43In your books write down sets of numbers from the table that you can total using all the addition strategies we have looked at today.