Grade 2

22 downloads 8363 Views 623KB Size Report
In this unit, children will use parts-and-total diagrams and change diagrams to help them organize information in addition stories that either “put together” or.
EM2007MM_G2_U03.qxd 12/6/05 4:11 PM Page 86 impos03 207:wg00004:wg00004_g2u03:layouts:

HOME LINK

Unit 4: Family Letter

39 

Addition and Subtraction In Unit 4, children will use addition and subtraction stories to develop mentalarithmetic skills. Mental arithmetic is computation done in one’s head or by drawing pictures, making tallies, or using manipulatives (counters, money, number lines, and number grids—no calculators, though). Children can also use their own solution strategies. A second grader uses a number grid to solve 5  9.

1

2

3

4

5

6

7

8

9 10

11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 Addition has two basic meanings: putting together and changing to more. In this unit, children will use parts-and-total diagrams and change diagrams to help them organize information in addition stories that either “put together” or “change to more.” See the vocabulary section on page 87 to learn more about these diagrams. Parts-and-Total Diagram

Total Change Diagram

?

Change Part

20

16

Start 20

End 6

Children will also develop estimation skills by solving problems that involve purchases. For example, your child will estimate whether $5.00 is enough to buy a pen that costs $1.69, a notebook that costs $2.25, and a ruler that costs 89¢. In the last part of this unit, children will learn paper-and-pencil strategies for addition and will continue to gain hands-on experience with thermometers, money, tape measures, and rulers. Home Links 4-8 and 4-9, which you will receive later, will give you more information on the paper-and-pencil strategies that your child will be learning. Please keep this Family Letter for reference as your child works through Unit 4.

86

?

Copyright © Wright Group/McGraw-Hill

Part

EM2007MM_G2_U03.qxd 12/6/05 4:11 PM Page 87 impos03 207:wg00004:wg00004_g2u03:layouts:

HOME LINK

3 9

Unit 4: Family Letter cont.

Vocabulary Important terms in Unit 4:

change-to-more number story A number story

parts-and-total diagram A diagram used to

having a starting quantity that is increased so the ending quantity is more than the starting quantity.

organize information in a parts-and-total number story. The parts-and-total diagram below organizes the information in Carl’s cookie story.

For example: Nick has 20 comic books. He buys 6 more. How many comic books does Nick have now?

Total

change diagram A device used to organize information in a change-to-more or change-to-less number story. The change diagram below organizes the information in Nick’s comic book story above.

?

Change Start 20

End 6

?

mental arithmetic Computation done totally or partially in one’s head, using a variety of strategies.

Part

Part

20

16

estimate (1) An answer close to, or approximating, an exact answer. (2) To make an estimate.

algorithm A step-by-step set of instructions for doing something—for example, for solving addition or subtraction problems.

parts-and-total number story A number story in which two or more quantities (parts) are combined to form a total quantity. For example: Carl baked 20 cookies. Sam baked 16 cookies. How many cookies did Carl and Sam bake in all?

Copyright © Wright Group/McGraw-Hill

Building Skills through Games In Unit 4, your child will practice addition and subtraction skills by playing the following games:

Addition Spin A “Spinner” and a ”Checker” take turns adding two numbers and checking the sum. After five turns, each player uses a calculator to find the sum of his or her scores. The player with the higher total wins.

Name That Number Each player turns over a card to find a number that must be renamed using any combination of five faceup cards.

Fact Extension Game Players find sums of 2-digit numbers and multiples of ten.

87

EM2007MM_G2_U03.qxd 12/6/05 4:11 PM Page 88 impos03 207:wg00004:wg00004_g2u03:layouts:

HOME LINK

39 

Unit 4: Family Letter cont.

Do-Anytime Activities To work with your child on the concepts taught in this unit and in previous units, try these interesting and rewarding activities: 1. Encourage your child to show you addition and subtraction strategies as these concepts are developed during the unit. 2. Make up number stories involving estimation. For example, pretend that your child has $2.00 and that he or she wants to buy a pencil marked 64¢, a tablet marked 98¢, and an eraser marked 29¢. Help your child estimate the total cost of the three items (without tax) and determine whether there is enough money to buy them. If appropriate, you can also ask your child to estimate the amount of change due. 3. Look at weather reports in the newspaper and on television and discuss differences between high and low temperatures. Also note the differences between the Fahrenheit and Celsius scales.

Copyright © Wright Group/McGraw-Hill

88

EM2007MM_G2_U03.qxd 12/6/05 4:11 PM Page 89 impos03 207:wg00004:wg00004_g2u03:layouts:

HOME LINK

Unit 4: Family Letter cont.

3 9

As You Help Your Child with Homework As your child brings home assignments, you may want to go over the instructions together, clarifying them as necessary. The answers listed below will guide you through this unit’s Home Links.

Home Link 41 1. 18 grapes; 11  7  18

10. 60

°F 11. 50

°F 12. 30

50

40

20

40

30

10

°F

2. 38 cards; 30  8  38 3. 52 pounds; 42  10  52 4. 27

5. 80

6. 83

7. 10

8. 17

9. 70

11. 66

12. 80

10. 30

Home Link 42 1. 47 pounds; 17  30  47 2. 75 pounds; 45  30  75 3. 60 pounds; 15  45  60

Home Link 43

Copyright © Wright Group/McGraw-Hill

60

°F

2.

90

°F

3.

20

50

80

10

40

70

0

30

60

10

20

50

20

4. a. 14

b. 13

14. 35

15. 97

16. 26

17. 50

18. 68

Home Link 45

4. 92 pounds; 17  45  30  92

1.

13. 70

c. 6

°C

1. no

2. yes

3. no

5. 100

6. 46

7. 47

Home Link 46 1. 30 marbles; 20  10  30 2. 54 cookies; 30  24  54 3. 100

4. 140

7. 94

8. 77

d. 15

Home Link 48 1. 76

2. 100

3. 83

4. 120

7. 93

8. 85

11. 169

12. 544

3. 83

4. 94

2. 34F

3. 52F

5. 98

6. 90

4. 96F

5. 48F

6. 73F

9. 71

10. 83

°F

9. 80

40

100

70

30

90

60

6. 83

2. About 20 inches

1. 20F

°F 8. 110

5. 79

Home Link 47

Home Link 44

7. 50

4. yes

°F

Home Link 49 1. 89

2. 108

5. 185

6. 363

89

Playing Everyday Math Games at Home for Grades K, 1, and 2 All games require one deck of regular playing cards (with Jokers removed) and can be played by 2-3 players or teams. If using the face cards, remind everyone that J = 11, Q = 12, and K = 13.

Top-It

K 1 2 Practices number recognition and comparing numbers

1. Shuffle the deck and place it face down in the center. 2. Each person takes one card from the top of the deck and says the number on the card. 3. The player who has the larger number takes both (or all, if 3 players) cards. If the cards show the same number, each player takes another card from the top of the deck. The player with the larger number then takes all of the cards facing up. 4. The game is over when all the cards have been taken. The player with more cards wins. Variation: If the face cards are confusing, remove them and play with just the cards from 1-10.

Concentration

K 1 2 Practices matching numbers and memorization

1. Use only 2 each of the cards 1-10 (20 cards total). 2. Shuffle the cards and place face down in 4 rows of 5 cards each. 3. The first player turns over any two cards. If the numbers on the cards match, the player takes the two cards and goes again. If the numbers don’t match, the player turns them back over after the other player has seen them. 4. The other player now turns over two cards and repeats the process. 5. The game ends when there are no more cards left. The winner is the player with more cards. Variation: Add more cards as the players improve (be sure to add them in pairs!).

Addition Top-It

K 1 2 Practices addition facts and comparing sums

1. Use the cards from 1-10. 2. Shuffle the deck and place it face down in the center. 3. Each player turns over 2 cards and calls out the sum of the numbers. Players should check each other’s sums. 4. The player with the greatest sum takes all the cards. In the case of a tie, each tied player turns over 2 more cards and calls out the sum. The player with the greater sum takes all of the cards from both plays. 5. Play ends when not enough cards are left for each player to have another turn. 6. The player who collected the most cards wins.

Name That Number

1. Use all of the cards. 2. Place the deck face down in the middle. Put five cards face up to the left of the deck. 3. Turn over the top card on the deck. This is the target K 1 2 number. 4. The first player tries to “name” the target number by adding or subtracting 2 of the 5 cards that are face Practices addition up. If the player is successful, he or she takes the and subtraction to target number and the other 2 cards used to name name numbers the target number. Those 3 cards are replaced by new cards from the deck. 5. If the player cannot name the target number, their turn is over and the next card on the top of the deck is turned over to be the target number. 6. The game is over when all of the cards in the deck have been turned over. Example: If the target number is 8 and the five cards showing are 3, 5, 9, and 13, two possible solutions are 5+3=8 13 – 5 = 8