adding and subtracting 2-digit numbers - everyday … to provide practice adding and subtracting...

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eToolkitePresentations Interactive Teacher’s

Lesson Guide

Algorithms Practice

EM FactsWorkshopGame™

Family Letters

CurriculumFocal Points

AssessmentManagement

Common Core State Standards

758 Unit 9 Place Value and Fractions

Advance PreparationYou may want to make a transparency of Home Link 9�3 to use when you go over the answers.

Teacher’s Reference Manual, Grades 1–3 p. 161

Key Concepts and Skills• Explain strategies used to solve problems

involving the addition and subtraction of

2-digit by 2-digit numbers.

[Operations and Computation Goal 2]

• Add and subtract 2-digit numbers using

strategies based on place value and the

relationship between addition and subtraction.


• Tell, write, and solve number stories.


• Write addition and subtraction number

sentences using +, -, and =.

[Patterns, Functions, and Algebra Goal 2]

• Use the properties of operations to add and

subtract 2-digit numbers.

[Patterns, Functions, and Algebra Goal 3]

Key ActivitiesChildren use the data on their animal cards

to make up and solve addition and

subtraction number stories.

Ongoing Assessment: Informing Instruction See page 760.

MaterialsMath Journal 2, p. 182

Home Link 9�3

slate � animal cards from Unit 5 � Number-

Grid Poster � base-10 blocks (optional)

Practicing with Name-Collection BoxesMath Masters, p. 262

Children use name-collection boxes to

find equivalent names for numbers.

Math Boxes 9 �4Math Journal 2, p. 183

Children practice and maintain skills

through Math Box problems.

Ongoing Assessment: Recognizing Student Achievement Use Math Boxes, Problem 3. [Number and Numeration Goal 4]

Home Link 9 �4Math Masters, p. 263

Children practice and maintain skills

through Home Link activities.

READINESS

Practicing 2-Digit Addition and Subtractionper partnership: 2 each of number cards 0–9

(from the Everything Math Deck, if available),

base-10 blocks (longs and cubes), 1 penny,

slate (optional)

Children use base-10 blocks to review adding

and subtracting 2-digit numbers.

ENRICHMENTComparing the Sums of 2-Digit by 2-Digit Addition Problemsanimal cards from Unit 5

Children solve two-digit addition problems

and compare the sums.

ELL SUPPORT

Comparing the Weights of Objectsper group: bath scale, objects to weigh

Children weigh objects and order and

compare weights.

Teaching the Lesson Ongoing Learning & Practice Differentiation Options

Adding and Subtracting 2-Digit Numbers

Objective To provide practice adding and subtracting

2-digit numbers.2

��

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1 Teaching the Lesson

� Math Message Follow-Up WHOLE-CLASS ACTIVITY

Briefly go over the answers. The rabbit is the shortest animal on the cards; the porpoise is the longest. Discuss the meaning of the words length and height. Make sure children understand that height is used to refer to how tall someone or something is. Length is the size of something from one end to the other.

� Creating and Solving WHOLE-CLASS ACTIVITY

Silly Animal Stories(Math Journal 2, p. 182)

Ask children to find the animal-card pictures of the rabbit and the raccoon. Then pose the following number story:

● Suppose the rabbit and the raccoon lie nose to nose. What will be their total length?

Have children share solution strategies. Some children may have added mentally and reasoned as follows: “Eleven is 1 more than 10. So I added 10 to 23; that’s 33. Then I added 1 more; that’s 34.” Demonstrate this strategy on the Number-Grid Poster: Start at 23, add 10 by moving down one row to 33, then add 1 by moving one space to 34.

Summarize the number story by drawing a parts-and-total diagram and writing a number model.

Ask children to make up number stories about comparing or finding total lengths or weights of two animals on their cards. Suggest that they imagine two animals on the same weighing scale or one animal sitting on top of another. To support English language learners, discuss the meanings of the words weight and scale.

ELL

PROBLEMBBBBBBBBBBOOOOOOOOOOOBBBBBBBBBBBBBBBBBBBBBBBBBBBB MMMMEEEEBLBLBLBLBLELLLLBLEBLEBLEBLEBLEBLEBLEEEMMMMMMMMMMMMMMOOOOOOOOOOOOBBBLBLBLBBBLLLLLLPROPROPROPROPROPROPROPROPROPROPROPRPPROPRPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPROROOROROROROROOPPPPPPP MMMMMMMMMMMMMMMMMMMMMMEEEEEEEEEEEEEEELEEELEEEEEEEELLLLLLLLLLLLLLLLLLLLLLRRRRRRRRRRRRRRRRRRPROBLEMSOLVING

BBBBBBBBBBBBBBBBBBBBB EEELEMMMMMMMMOOOOOOOOOOBBBBLBLBLBLBBLBBROOOROROROROROROROROROROO LELELELEEEEEELEMMMMMMMMMMMMLEMLLLLLLLLLLLLLLLLLLLLRRRRRRRRRRRGGGGLLLLLLLLLLLLLVVINVINVINVINVINNNNVINVINNVINVINVINVINV GGGGGGGGGGGOOOOLOLOLOOLOO VINVINVINVLLLLLLLLLVINVINVINVINVINVINVINVINVINVINVINVINVINV NGGGGGGGGGGOLOLOLOLOLOLOLOOOLO VVVVLLLLLLLLLLVVVVVVVVVVOOSOSOSOSOSOSOSOSOSOSOSOSOSOOOOOSOSOSOSOSOSOSOSOSOSOSOSOOSOSOSOSOSOSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSS VVVVVVVVVVVVVVVVVVVVVVLLLLVVVVVVVVLLLVVVVVVVLLLLLLLVVVVLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLSSSSSSSSSSSSSSSSSSSSS GGGGGGGGGGGGGGGGGGGOOOOOOOOOOOOOOOOOOOO GGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGNNNNNNNNNNNNNNNNNNNNNNNNNNNIIIIIIIIIIIIIIIIIIISOLVING

Math Journal 2, p. 182

Student Page

Lesson 9�4 759

Getting Started

Math MessageTake out your animal cards. Look at the side that shows the animal’s length in inches. Which animal is the shortest? Which is the longest?

Home Link 9�3 Follow-Up Briefly go over the answers. Ask children to describe how they used number-grid patterns to help them complete the puzzles.

Mental Math and ReflexesHave children answer the following rounding questions on their slates:

Is 17 closer to 10 or 20? 20 Is 24 closer to 20 or 30? 20

What multiple of 10 is closest to 33? 30 To 68? 70 To 86? 90

Is 120 closer to 100 or 200? 100 Is 175 closer to 100 or 200? 200

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10 + 10 + 5

50 - 20

3 dimes

Sample answers:‰ Â 33 - 3

LESSON

9�4

Name Date

Name-Collection Boxes

1. Add 5 names. 2. Fill in the label. Add 5 names.

3. Cross out names that do 4. Cross out names that do not not belong. belong. Add 2 names.

Answers vary.

33 25

10 + 15Answers vary.

30 3 + 3 + 3 + 3

‰ ‰60 - 1010 + 10 + 10 + 10 + 10

////\ ////\ ////\ ////\ ////\

25 + 2550

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Math Masters, p. 262

Teaching Master


Adjusting the Activity

Suggested number stories:

● If the koala stood on top of the penguin’s head, how tall would they be together? 60 in.

● If the fox sat on top of the beaver, how much would they weigh together? 70 lb

● How much taller is the boy than the girl? 7 in.

● How much more does the cheetah weigh than the boy? 70 lb

Tell children to solve the number stories any way they can. Encourage children to use concrete models, such as base-10 blocks, and drawings to solve the problems. Have children share their solution strategies, and encourage them to try new strategies on subsequent number stories. For instance, you may wish to have children practice some common addition and subtraction strategies with the following number stories:

● Counting on from the larger addend: How much do the 15 lb eagle and the 7 lb cat weigh together? Start with the larger weight, 15 lb, and count up 7 lb to get 22 lb total.

● Making ten: If the 48 in. cheetah and the 23 in. raccoon sleep head-to-toe in a line, how long would they be together? Use base-10 blocks to represent the cheetah’s length (4 longs, 8 cubes) and the raccoon’s length (2 longs, 3 cubes). Add tens to tens and ones to ones to get 6 longs, 11 cubes. Trade 10 cubes for one long, composing a new ten and leaving 1 cube left over. The length is 7 tens, 1 one, or 71 inches total.

● Counting up to subtract: How much more does the 50 lb boy weigh than the 41 lb girl? Count up from 41 lb to 50 lb, a 9 lb difference.

When discussing solutions, display the appropriate unit box on the board. Ask children to suggest a number model for the problem. Keep in mind that more than one model may be appropriate. For example, when comparing the heights of the boy and the girl, the counting-up strategy can be represented by the addition number model 43 + 7 = 50 or the subtraction number model 50 – 43 = 7. Summarize with an appropriate situation diagram.

Have children model the number stories with base-10 blocks as they did

in Lesson 5-5 with animal weight number stories.

A U D I T O R Y � K I N E S T H E T I C � T A C T I L E � V I S U A L

Ongoing Assessment: Informing Instruction

Watch for children who have trouble deciding whether to add or subtract when

solving a number story. Suggest that they act out the number story in order to

better understand the situation. You may also want to help children select a

situation diagram that fits the story.

ELL

first-grade girl 43 in. 41 lb

7-year-old boy 50 in. 50 lb

cheetah 48 in. 120 lb

porpoise 72 in. 98 lb

penguin 36 in. 75 lb

beaver 30 in. 56 lb

fox 20 in. 14 lb

cat 12 in. 7 lb

raccoon 23 in. 23 lb

koala 24 in. 19 lb

eagle 35 in. 15 lb

rabbit 11 in. 6 lb

Animal card heights, lengths, and weights

Links to the FutureChildren practice solving number stories that

include 2-digit by 2-digit addition and

subtraction. In first grade, children should be

able to solve and explain strategies for solving

2-digit by 1-digit number stories; however,

solving 2-digit by 2-digit addition and

subtraction number stories is a Grade 2 Goal.

�

�

�


Math Boxes

Date

LESSON

9 � 4

3. Draw 12 dimes. Use Ís. Shade 1 _ 4 of the dimes.

4. A toy dinosaur costs 89¢. I paid $1.00. How much change do

I get? ¢ Show this amount with Í,

Â, and Î.

2. Solve. 16 - 9 = 26 - 9 = 56 - 9 = 106 - 9 =

6. Circle the 3 polygons.

5. Find the rule. Fill in the missing numbers.

32

14

98, 99

52, 53

1. Use your number grid. Start at 48. Count back 15. 48 - 15 = ? Fill in the circle next to the

best answer.A 43 B 33C 63 D 36

Rule

165 265 365

717

11

4797

Sample answer:ÍÎ

Add 100 465 565

�

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Math Journal 2, p. 183

Student Page

Lesson 9�4 761

After children have solved a few number stories as a class, divide the class into partnerships. Partners use their animal cards to make up and record two silly stories on journal page 182.

NOTE While children should learn to add and subtract on the number grid, they

should also be encouraged to be flexible in their solution strategies. For example,

there is no need for them to turn to the number grid, or any other aid, if they are

able to find a correct answer mentally. There will also be times when a visual

representation of a problem with pictures, doodles, counters, or base-10 blocks

will result in a better understanding of its solution. Emphasizing the use of the

number grid as a device for checking answers will, it is hoped, discourage

children from relying solely on the number grid to fi nd answers.

Select a few of the children’s silly animal stories to act out with the class. Ask children to write the number model that matches the story.

Ask your child to explain how to solve the first set of problems with base-10 blocks and the second set on the number grid. At this point it is important that children work with more concrete representations. This will be beneficial later, when they are faced with more difficult problems.

Please return this Home Link to school tomorrow.

Family Note

HOME LINK

9�4

Name Date

Solving Problems Two Ways

Draw the total number of base-10 blocks. Then write the total.Example: || | ||.. + |||..... = | || | || ||.......

52 + 35 = 87 1. |..... + ||||||.. = 15 + 62 = 2. || |.... + ||.... = 34 + 24 = Use the number grid to help you solve the problems.

3. 63 + 8 =

4. 55 + 20 =

5. = 47 + 12

|||||........

| || | || |.......

75

71

58

77

6. It is 8:10. How many minutes is it until 8:30?

minutes20

51 52 54 55 56 57 58 59 6061 62 63 64 65 66 67 68 69 7071 72 73 74 75 76 77 78 79 8081 82 83 84 85 86 87 88 89 9091 92 93 94 95 96 97 98 99 100

01 2 3 4 5 6 7 8 9 10

11 12 13 14 15 16 17 18 19 2021 22 23 24 25 26 27 28 29 3031 32 33 34 35 36 37 38 39 4041 42 43 44 45 46 47 48 49 50

53

�1�2�3�4�5�6�7�8�9

Practice

10, 11,29

59

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Math Masters, p. 263

Home Link Master

2 Ongoing Learning & Practice

� Practicing with Name-Collection INDEPENDENTACTIVITY

Boxes(Math Masters, p. 262)

Use Math Masters, page 262 to provide practice with name-collection boxes.

� Math Boxes 9�4 INDEPENDENTACTIVITY

(Math Journal 2, p. 183)

Mixed Practice Math Boxes in this lesson are paired with Math Boxes in Lesson 9-2. The skills in Problem 6 preview Unit 10 content.

Ongoing Assessment: Math Boxes

Problem 3 �Recognizing Student Achievement

Use Math Boxes, Problem 3 to assess children’s ability to find fractions of a set.

Children are making adequate progress if they are able to shade 1

_ 4 of the dimes.

[Number and Numeration Goal 4]

� Home Link 9�4 INDEPENDENTACTIVITY

(Math Masters, p. 263)

Home Connection Children solve 2-digit addition problems with the help of a number grid and base-10 block illustrations.



3 Differentiation Options

READINESS PARTNER ACTIVITY

� Practicing 2-Digit Addition 5–15 Min

and Subtraction

To explore adding and subtracting 2-digit numbers using a concrete model, have partners use base-10 blocks. Each child turns over two number cards to create a 2-digit number and then represents that number with base-10 blocks. Next, partners flip a penny to determine whether to add or subtract—heads, they add; tails, they subtract. They work together to add or subtract the two 2-digit numbers. Children can record number models on their slates.

ENRICHMENT PARTNER ACTIVITY

� Comparing the Sums of 2-Digit 5–15 Min

by 2-Digit Addition Problems

To further explore 2-digit by 2-digit addition, children play a variation of Addition Top-It using the animal-length cards. Partners combine their decks of animal cards and place them in a stack on the table, length-side down. Each partner turns over 2 cards and finds the sum of the lengths. Partners compare their sums. The partner with the higher sum takes all 4 cards. The game is over when all of the cards from the stack have been played.

ELL SUPPORT SMALL-GROUP ACTIVITY

� Comparing the Weights 5–15 Min

of Objects

To provide language support for weight, provide children with opportunities to weigh a variety of objects using a bath scale. Label the names of the objects and then ask children to label the weights in pounds. Provide children with opportunities to hold the objects as they compare the weights. Ask them to list the weights in order from lightest to heaviest. Ask children to find an object that weighs about one pound.

Planning Ahead

For Lesson 9-5, you will need containers, a pourable substance such as unpopped popcorn, rice, or dried beans, 3 large cups, and 3 small cups. See the materials list for Part 1 in Lesson 9-5.

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adding and subtracting 2-digit numbers - everyday … to provide practice adding and subtracting...

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