Today's topic: two different strategies to make arithmetic easier.

I. From the beginning of the 3rd grade Everyday Mathematics Student Math Journal, volume 1, p. 15:

Math Message

Use your calculator

1. Sharon read the first 11 pages of her book last week. She read the rest of the book this week. If she read 86 pages week, how many pages long is her book?

Answer: Her book is _______________ pages long.

Number model: ______________________________________________

2. The paper clip was invented in 1868. The stapler was invented in 1900. How many years after the paper clip was the stapler invented?

Answer: The stapler was invented ____________ years later.

Number model: ______________________________________________

3. 28 + 64 + 39 + 42 = __________

4. 2,648 - 1, 576 = ___________

Calculator Practice

Use your calculator.

5. Begin at 25. Count up by 6s. Record your counts below.

25 ___ ___ ___ ___ ___ ___ ___ ___ ___ ___ ___ ___

6. Begin at 90. Count back by 9s:

90 ___ ___ ___ ___ ___ ___ ___ ___ ___

Solve the calculator puzzles. Remember to add or subtract to find the "Change to" number.

7.

Enter __ Change to ___ How?

_42_______52___________

_61_______41____________

_145______105___________

8.

Enter __ Change to ___ How?

_178_______208_________

1604_______804_________

_722______3722_________

II. From the beginning of the 3rd grade Singapore Math Primary Mathematics 3A, p. 26:

1. Fill in the blanks.

(a) 59 + 6 = 60 + _____

(b) 42 + 3 = 40 + _____

(c) 38 + 4 = _____ +2

(d) 65 + 5 = _____+ 0

(e) 25 + 7 = 30 + _____

(f) 46+ 6 = _____ + 2

2. Add.

(a) 42 --- + 50 ---> _____

(b) 53 --- + 30 ---> _____

3. Add.

(a) 84 + 7 =

(b) 48 + 9 =

(c) 18 + 80 =

(d) 25 + 70 =

4. Add

(a) 58 + 34 =

(b) 46 + 24 =

(c) 24 + 68 =

(d) 47 + 62 =

III. Extra Credit

There is no calculator practice in Singapore Math. What are Singapore Math students missing?

## 2 comments:

Number model: how about set theory with ur-elements? Or wait -- do I really need ur-elements to construct a model of the integers! This question is making me really think?

They are missing the creation of a crutch.

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