## Thursday, January 22, 2009

### Math problems of the week: 2nd grade Investigations vs. Singapore Math

1. From "Stickers, Number Strings, and Story Problems," tonight's Investigations homework:

Can you make ...?

Use three different numbers in each problem.
Use each number below at least once.

7, 8, 9, 1, 4
5, 3, 6, 2

1. Can you make 15 with 3 numbers?

_____ + _____ + _____ = 15

2. Can you make 16 with 3 numbers?

_____ + _____ + _____ = 16

3. Can you make 17 with 3 numbers?

_____ + _____ + _____ = 17

4. Can you make 18 with 3 numbers?

_____ + _____ + _____ = 18

2. From the middle of the 2nd grade Singapore Math curriculum, Primary Mathematics 2B, p. 17

(a) 183 + 99 =
(b) 246 + 98 =
(c) 199 + 99 =
(d) 206 + 98 =
(e) 99 + 556 =
(f) 98 + 235 =
(g) 99 + 408 =
(h) 98 + 399 =

3. Extra Credit:

1. For each problem set, relate the language arts challenge (understanding the directions) to the mathematical challenge.

2. Which problem set teaches a more useful mathematical skill? Compare the real-life and mathematical utility of:

a. Thinking of ways to "make" a two-digit number with three one-digit numbers, using each number at least once.
b. Adding different numbers that approach 100 to various two and three digit numbers and seeing the effects on place value.