2nd grade - njctlcontent.njctl.org/courses/math/2nd-grade/2-digit...dec 09, 2015 · addition...
TRANSCRIPT
Slide 1 / 137 Slide 2 / 137
2nd Grade
2 Digit Addition and Subtraction
2015-12-03
www.njctl.org
Slide 3 / 137
click on a topic to go to that section
Table of ContentsPresentation 2
Addition
Subtraction
Mixed Addition and Subtraction Practice
Mentally adding and subtracting 10 and 100
Lab: Give and Take
Slide 4 / 137
Standards for Mathematical Practices
MP8 Look for and express regularity in repeated reasoning.
MP1 Make sense of problems and persevere in solving them.
MP2 Reason abstractly and quantitatively.
MP3 Construct viable arguments and critique the reasoning of others.
MP4 Model with mathematics.
MP5 Use appropriate tools strategically.
MP6 Attend to precision.
MP7 Look for and make use of structure.
Click on each standard to bring you to an example of how to meet
this standard within the unit.
Slide 5 / 137click on a
topic to go to that section
Subtraction
2 Digit Subtraction without Regrouping
Regrouping with Base Ten Blocks
Subtraction Word Problems with Regrouping
Subtraction Practice
Click to return to mainTable of Contents
2 Digit Word Problems without Regrouping
Regrouping without Base Ten Blocks
Slide 6 / 137
2-Digit SubtractionWithout Regrouping
Click to return to SubtractionTable of Contents
Slide 7 / 137
What number is shown?
2 Digit Subtraction
Slide 8 / 137
Now we want to subtract 14.
When we subtract, we take away.ALWAYS start with the bigger number when you subtract.
2 Digit Subtraction
Slide 9 / 137
tens ones
2 71 4-
Just like when we added, you need to line up the two numbers.
2 Digit Subtraction
The ones are stacked and so are the tens.
Slide 10 / 137
tens ones
2 71 4-
Next, subtract the ones by crossing them out.
How many are left?
2 Digit Subtraction
Slide 11 / 137
tens ones
2 71 4-
Next, cross out the tens.
How many are left?
3
2 Digit Subtraction
Slide 12 / 137
tens ones
2 71 4-
31
2 Digit Subtraction
Slide 13 / 137
What number is shown?
2 Digit Subtraction
Slide 14 / 137
Let's subtract 20Our subtraction number model is:
32 - 20 =
2 Digit Subtraction
Slide 15 / 137
tens ones
3 22 0-
Rewriting it makes it easier to subtract.
2 Digit Subtraction
What do we subtract first?
Slide 16 / 137
tens ones
3 22 0-
2
What is the next step?
2 Digit Subtraction
Slide 17 / 137
tens ones
3 22 0-
21
2 Digit SubtractionSlide 18 / 137
8562-
What do we do first?
2 Digit Subtraction
If there is not a place value chart, it may help to draw a line between the tens and ones to keep them seperated.
Slide 19 / 137
8562-
Now what do we do?
3
2 Digit Subtraction
Slide 20 / 137
8562-
What is the answer?
32
2 Digit Subtraction
Slide 21 / 137
76- 26
2 Digit Subtraction
Slide 22 / 137
68 - 24 =
What should we do to this subtraction problem to make it easier to answer?
2 Digit Subtraction
Slide 23 / 137
68 - 24
2 Digit Subtraction
Slide 24 / 137
-Roll all 4 dice and then subtract the numbers.
2 Digit Subtraction
Slide 25 / 137
1 If you take away 70, is the answer 24?
Yes
No
Slide 26 / 137
2 If you take 12 away from this number, is the difference 7?
Yes
No
Slide 27 / 137
3 Take away 83. What is the difference?
Slide 28 / 137
4 Take 32 away from this number, what is the difference?
Slide 29 / 137
5 What is the difference 67 - 47 = ?
Slide 30 / 137
Slide 31 / 137 Slide 32 / 137
2 Digit Word Problems Without Regrouping
Click to return to Table of Contents
Slide 33 / 137
There are 24 children in a play. 11 children dance.The other children sing. How many children sing?
Word Problems
Slide 34 / 137
How many singers?
24 children in all
There are 24 children in a play. 11 children dance.The other children sing. How many children sing?
11 dancers
Word Problems
Slide 35 / 137
To find the difference, subtract:
24- 11
Remember:
1. Subtract the ones2. Subtract the tens
Word Problems
Slide 36 / 137
Number Model
24 - 11 = 13 or 24- 11
13
Where is the bigger number in each problem?
Slide 37 / 137
How can we find the answer?
There are 37 chairs at the play. There are 13 couches.
How many more chairs than couches are there?
Word Problems
Slide 38 / 137
Zachary sold 28 tickets for the play.Patrick sold 15 tickets. How many
more tickets did Zachary sell than Patrick?
Practice
Slide 39 / 137
On Friday, 49 people came to the play. OnSaturday, 25 fewer people came. How many
came on Saturday?
Practice
Slide 40 / 137
6 There are 28 girls and 16 boys in the class. How many more girls than boys are in the class?
A 12
B 14
C 36
D 46
Slide 41 / 137
7 Britney sold 39 boxes of popcorn and 18 sodas. How many more boxes of popcorn than sodas did she sell?
A 11
B 18
C 21
D 26
Slide 42 / 137
8 There are 34 geese and 24 ducks in a pond. How many more geese than ducks are there?
Slide 43 / 137
9 There are 41 seagulls on the beach. Then 30 fly away. How many are left?
Slide 44 / 137
10 Henry has 45 stamps. He gives 13 to Julie. How many stamps does he have left?
Quiz
Slide 45 / 137 Slide 46 / 137
Slide 47 / 137
Regroupingwith Base Ten Blocks
Click to return to SubtractionTable of Contents
Slide 48 / 137
What number is shown?
Regrouping
Slide 49 / 137
33 - 8 = ?Now we want to subtract 8.
What do we do first?
Regrouping
Slide 50 / 137
How can we get more ones without changing the total
number?
We have to take 8 ones away, but we do not have enough.
33 8-
Regrouping
Slide 51 / 137
33 - 8 = Now you can subtract!!!
Cross out the ones that you take away.
Regrouping
What is the difference?
Slide 52 / 137
52 - 7 = ?What do we need to do?
Regrouping
Slide 53 / 137
Look at the problem below. Do you need to regroup? How do you know?
63 - 9 = ?
Regrouping
Slide 54 / 137
Look at the problem below. First, decide is you need to regroup.
41 - 5 = ?
Regrouping
Slide 55 / 137
Look at the problem below. First, decide is you need to regroup.
83 - 2 = ?
Regrouping
Slide 56 / 137
Look at the problem below. First, decide is you need to regroup.
46 - 22 = ?
Regrouping
Slide 57 / 137
Look at the problem below. Draw base ten blocks to help you
solve the problem.
35 - 7 = ?
Regrouping
Slide 58 / 137
Look at the problem below. Draw base ten blocks to help you
solve the problem.
11 - 3 = ?
Regrouping
Slide 59 / 137
How will you know if you have to regroup?
Regrouping
Slide 60 / 137
11 Which TWO problems require you to regroup?
A 57 - 3 = ?
B 38 - 9 = ?
C 13 - 5 = ?
D 40 - 0 = ?
Slide 61 / 137
12 Do you need to regroup?
45 - 8 = ?
Yes
No
Slide 62 / 137
13 Do you need to regroup?
67 - 8 = ?
Yes
No
Slide 63 / 137
14
56
- 8Use base ten blocks at your seat to help you
Slide 64 / 137
15
93
- 14Use base ten blocks at your seat to help you
Slide 65 / 137 Slide 66 / 137
Slide 67 / 137
Regroupingwithout Base Ten Blocks
Click to return to SubtractionTable of Contents
Slide 68 / 137
tens ones
3 31 8-
Regrouping
Look at the problem. What do we need to do first?
Slide 69 / 137
tens ones
3 31 8-
RegroupingBefore we subtract, we need to make sure the written problem matches the
base ten blocks.
Slide 70 / 137
tens ones
3 31 8-
RegroupingBefore we subtract, we need to make sure the written problem matches the
base ten blocks.
2 13
Slide 71 / 137
tens ones
5 23 7-
Start with the ones.Can we take 7 away from 2?
What do we need to do?
Regrouping
Slide 72 / 137
Let's Practice!
tens ones
-6 9
75
Base Ten Blocks
Slide 73 / 137
Let's Practice!
tens ones
-
Base Ten Blocks
70 - 35 =
Slide 74 / 137
No Blocks!
How can we solve this problem without base ten blocks?
5 2 3 6-
tens ones
Slide 75 / 137
No Blocks!
Now let's subtract!
5 2 3 6-
tens ones
124
Slide 76 / 137
Practice
6 0 2 7-
tens ones
Slide 77 / 137
Practice
9 47 8-
tens ones
Slide 78 / 137
2512-
-7436
Remember!
More on top?No need to stop!
More on the floor?Go next door!
Numbers the same?Zeros the name! -
8161
Regrouping
Slide 79 / 137
Change the columns to 2 prior to starting
Click on the picture below for more practice on the National Library of Virtual Manipulatives site.
Slide 80 / 137
16 85- 37 48
Yes
No
Slide 81 / 137
17 94 - 25 = 71
Yes
No
Slide 82 / 137
18 67- 58
Slide 83 / 137
19 88 - 34 =
Slide 84 / 137
20 42 - 7 =
Slide 85 / 137
21 34- 26
Slide 86 / 137
Slide 87 / 137 Slide 88 / 137
Word Problems with Regrouping
Click to return to SubtractionTable of Contents
Slide 89 / 137
What do we have to doto find the answer?
There are 65 students on the playground.47 are wearing sneakers. How many are
not wearing sneakers?
Word Problems
Slide 90 / 137
tens ones
6 5 4 7-
Is there "more on the floor?"
Regrouping
Slide 91 / 137
tens ones
6 5 4 7-
We can not take 7 awayfrom 5, so we have to regroup 1 ten as 10
ones.
What do we do now?
155
Regrouping
Slide 92 / 137
tens ones
6 5 4 7-
155
8
Regrouping
What is the next step?
Slide 93 / 137
One day 45 cars and 19 trucks were washed at the car wash. How many more cars than trucks were washed?
What do we have to doto find the answer?
Word Problems
Slide 94 / 137
How do I subtract?
4 5 1 9
Regrouping
tens ones
-
Slide 95 / 137
There are 83 students eating lunch. 55 are eating hot lunch. How manystudents are not eating hot lunch?
Word Problems
Slide 96 / 137
A soda cost 75 cents. Mr. Westhas 46 cents. How many more cents does he need for a soda?
Word Problems
Slide 97 / 137
22 There are 50 students in the library. 27 of them are wearing blue. How many are not wearing blue?
A 33
B 37
C 23
D 77
Slide 98 / 137
23 Colin had 32 baseball cards. He sold 16. How many were left?
Slide 99 / 137
24 Megan had 73 books at the yard sale. She sold 42. How many are left?
A 31
B 115
C 211
D 35
Slide 100 / 137
25 The pet store has 58 fish. They sell 39 fish. How many fish are left at the pet store?
Slide 101 / 137
26 In art class, Jeff made 61 paper moons. Kelly made 9. How many more moons did Jeff make?
Slide 102 / 137
Slide 103 / 137 Slide 104 / 137
Subtraction Practice
Click to return to SubtractionTable of Contents
Slide 105 / 137
How can we write this problem to find the difference?
There are 84 apples on theapple tree. Sara picks 68
apples. How many apples are left on the tree?
Word Problems
Slide 106 / 137
8468-
YES!Do we have to regroup?
There is more on the floor.
Regroup 1 ten for 10 ones
Subtract the ones first,then the tens.
How do you know?
What do we do first?
What do we do next?
Click each box tocheck your answer
Practice
Slide 107 / 137 Slide 108 / 137
3715-
NO!Do we have to regroup?
There is more on top.
Subtract the ones.
Subtract the tens.
How do you know?
What do we do first?
What do we do next?
Click each box tocheck your answer
Review
Slide 109 / 137
Jenna picks up 34 sea shells.She puts 17 of them in a box.
How many does she have left?
Word Problems
Slide 110 / 137
Sadie buys 74 pieces of paper.She uses 44 for her book.
How many pieces of paper are left?
Word Problems
Slide 111 / 137
27 Mom bakes 23 cupcakes. She decorates 19 purple and the rest blue. How many were blue?
A 16
B 4
C 14
D 34
Slide 112 / 137
28 Becky buys 57 apples and oranges. 23 are oranges. How many are apples?
A 23
B 53
C 57
D 34
Pick the correct answer from each column to complete the subtraction sentence for this word problem.
_______ - _______ = 34
E 23
F 53
G 57
H 34
Slide 113 / 137
29 Kira can jump a rope 94 times. Myah can jump a rope 79 times. How many more times can Kira jump than Myah?
Slide 114 / 137
30 The team scored 74 points. Shawn scored 36 of the points. How many points did the rest of the team score?
Slide 115 / 137
31 There are 49 markers in the box. 14 of them are being used. How many are left in the box?
Quiz
Slide 116 / 137
Slide 117 / 137 Slide 118 / 137
Mixed Practice
Click to return to mainTable of Contents
Slide 119 / 137
There are 78 people wearing blue hats and 35 people wearing red
hats. How many hats in all?
Addition
The question askshow many in all
Line up our numbers to add
Is this an addition or subtraction problem?
How do we know?
What do we have todo to find the answer?
Word Problems
Slide 120 / 137
7835+
What do we add first?
Practice
Slide 121 / 137
7835+
8 + 5 = Now what do we do?
Practice
Slide 122 / 137
7835+
Now what do we do?
3
1
Practice
Slide 123 / 137
7835+
3
11 + 7 + 3 =
Practice
Slide 124 / 137
7835+
311
1
Practice
Slide 125 / 137
The paint store has 64 cans of paint. They sell 55 cans. How
many cans are left?
SubtractionIs this an addition or subtraction problem?
The problem talks about takingaway and asks how many are left.How do we know?
Line up the numbers,with the biggest number
on top to subtract.
What do we have todo to find the answer?
Click each boxto check the
answer
Practice
Slide 126 / 137
6455-
Practice
Slide 127 / 137
3558+
Practice
Slide 128 / 137
What clue words tell us what kind of problem this is?
There are 50 blue birds and 86 red birds.How many birds are there all together?
Practice
Slide 129 / 137
Two boys collected a total of 43 rocks. If John collected 22, how
many did Dave collect?
Practice
Slide 130 / 137
32 Kurt has 70 pennies. He gives Jay 48 pennies. How many pennies does he have left?
A 38
B 22
C 118
D 32
Slide 131 / 137
33 Jenny does 29 jumping jacks. Nicole does 33 jumping jacks. How many jumping jacks did they do all together?
A 52
B 16
C 62
D 4
Slide 132 / 137
34 There are 56 yellow flowers and 53 red flowers. How many flowers in all?
Slide 133 / 137
35 There are 38 kids that have brown eyes and 27 kids that have blue eyes. How many more kids have brown eyes?
Slide 134 / 137
36 Jack has to drive 82 miles. He already drove 47 miles. How many more miles does Jack have to drive?
Slide 135 / 137
Lab: Give and Take
Practice regrouping/ trading “tens” and “ones” while playing this game
Click here for complete directions
Click to return to mainTable of Contents
Slide 136 / 137
Slide 137 / 137