CONFIDENTIAL 1 Let's review what we learned in our last lesson. *We learned about doubling a...

CONFIDENTIAL 1

Let's review what we learned in our last lesson.

*We learned about doubling a number*We also learned about grouping numbers into groups of 10 to add easier

*We talked about the different properties of addition:Commutative: order 14 + 27= 27 + 14Associative: grouping 25 + (15 + 2) =(25 + 15) + 2Identity: zero 45 + 0 = 45

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Good Afternoon

CONFIDENTIAL 2

1.) Find the next number in the pattern.22, 24, 26, 28, ____

2.) Order these numbers from least to greatest.67 45 89 76

3.) 16 + 16 =

Let’s see what you remember

CONFIDENTIAL 3

Today we are going to learn about Subtraction.

You might have heard these words to use subtraction: Take away, minus, fewer than, more than, or less.

What is subtraction? Subtraction is when you take a smaller number from a larger number.

CONFIDENTIAL 4

When we subtract numbers we can either count back for smaller

numbers

8-3 5

8 7 6 5

CONFIDENTIAL 5

Now for larger numbers we can count up

10-6

4

66

6 7 8 9 10

Addition is always easier thansubtraction

Think: start at 6 and count up to 10, how many do you count up?

CONFIDENTIAL 6

Your turn to try some

15-7

10-4

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Addition and Subtraction are opposites of each other.

Do you know what opposite means? Hot and cold are opposite words

So are up and down. So if addition and subtraction are opposites, that means

they each use fact families.

Let’s do an addition problem to find the opposite subtraction problem

6 +8 = 14 8 + 6 = 14 (Remember, these are also using the Commutative Property)

CONFIDENTIAL 8

1. If we know the addition problem, 6 + 8 = 14 then…

2. We can find the subtraction problem. 14-8 = 6 or 14 – 6 = 8

Do you see how we used the Commutative Property again?

These are called fact families. You use only 3 numbers.

CONFIDENTIAL 9

Subtraction

When you subtract, you start with the larger number and then put the other 2 numbers: One will be the answer.

5 7 12

12-5

7

12 -7

5

You can check subtraction by adding the 2 numbers together5 + 7 = 12

CONFIDENTIAL 10

You try a couple.. Make a subtraction sentence with each set of numbers.

14 5 9 3 10 7

CONFIDENTIAL 11

You can also find the 3rd number, by thinking what number added to this number = the answer?

18   -

10     

So 10 + ? = 18

10 + 8 = 18

CONFIDENTIAL 12

Find the missing number

15 - 9 = 27

-

24

CONFIDENTIAL 13

Break!

CONFIDENTIAL 14Title: PuzzleFormat: WebEx Web BrowserDouble-click to edit

CONFIDENTIAL 15

Regrouping to subtract

 2   tens    4   ones    - 8 ones

You can’t take 8 ones from 4 ones so you have to regroup a set of 10’s

2 tens 4 ones   1   ten    14   ones

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1 ten 14 ones - 8 ones

= 1 ten 6 ones

-

CONFIDENTIAL 17

Your turn

 7   tens    8   ones    = ___ tens  ___ ones

CONFIDENTIAL 18

Subtracting 1 digit from 2 digits with regrouping.

72- 8 64

Sometimes this is also called borrowing. You are borrowing a group of 10 from the 10’s column

126

CONFIDENTIAL 19

Your Turn!Your Turn!22 -  2 =

 95 -  6 = 

57 -  9 =

CONFIDENTIAL 20

Assessment

1.) What are some words for subtraction?

2.)Which is easier for you: to count up or to count back?

3.) If you had this addition problem

15 + 4 = 19 What would the subtraction problems be?

4) Could you answer this subtraction problem 25 – ? = 21

21 + ? = 25 and then what would the number be?

CONFIDENTIAL 21

5.)What is the answer

47-9

6) . Carol had 18 candies and ate 7. How many does she have left?

CONFIDENTIAL 22

Let’s review•We learned the vocabulary words for subtraction•We learned that you can count back or count up to subtract•We learned that subtraction is the opposite of addition•We learned about fact families:•We found the missing number in subtraction problems: by thinking what number added to what number = the answer•We learned how to regroup or borrow to subtract numbers

CONFIDENTIAL 23

You did a GREAT job today!