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Unformatted text preview: 2. 3. Chapter. 3 OBJECTIVE: Represent subtraction using a set
You Will Need: Materials Card 3.4 USED
[3. D Paul has 15 postage stamps. lfhe gives 8 stamps to his sister. Rebecca. how many
stamps will he have then? . ' Using the squares from Materials Card 3.4. demonstrate how
you could model the following arithmetic problems concretely. Write an arithmetic expression and give the result. a. b. Estella has 13 postage stamps. If she gives some stamps to her friend. Rosa. she will
have 8 stamps left. How many stamps did she give to Rosa? c. Elie has 9 crackers and 6 pieces of cheese to put on the crackers. How many crackers
will not have. cheese on them? d. Anna wants to collect the trading cards of all 12 members of the Chicago Bulls. 11' she
now has 7 cards. how many more does she need to collect? e. Zia has a certain number of baseball trading cards. If he collects 8 more. he will have
17 cards. How many cards does he now have? - Howaretheproblemsinpartlsimilar? How are they different? Why might problem lie) be more diﬁicult for them? ‘54 Whole Numbers - and _ 41 l. OBJECTIVE: Represent subtraction using a measurement model
You Will Need: Your centimeter strips (Activity 3. 1] 4—— D-DalkGrssn—b To build albird house. Maxime needs a
board 25 cm long which he will cut from a
larger board. This "take-away” approach
can be modeled with your centimeter strips.
For example. imagine that a blue strip is
the larger board and a dark green
centimeter strip represents the length he
will cut off. lithe blue strip were shortened by taking away the length of the dark green
as pictured. how long is the result E - D? - D=DaIkGrssn Use this take-away approach to ﬁnd the following diﬁ'erences.
a. 0-1“: h. (0+RJ—Ks‘ c. [0+P}-D-= Marcie lives 13 blocks from the mall. If she has walked 6 blocks toward the mall. how many more blocks must she walk to reach the mail? In this case. we are looking for what
needs to be added to 6 to obtain the result of 13. The picture bel0w illustrates how this approach would ﬁnd E - D. Use your strips to solve the following: a. Y+__=0 b. K+__=O+R c. D+__=O+P ._ in these problems. you were looking for the
"missing addend.‘ How do the addition problems in part 3 relate to the subtraction
problems in part 2?” E: Rewrite each of the following subtraction problems into its missing-addend equivalent and
ﬁnd the solution. a. N-R=_ b. K~D=___ c. (0+W]-Y=_ The table to the right is the one you should
have obtained in Activity 3.2. Using the
mlssing-addend approach and this table. ﬁnd the following diil'erences.
a. N-Y=— b. O-Y=—
C. K-P= d. P-R=____ Use your centimeter strips to check
your results. ...
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- Spring '11