Grade 3-5

Multiply by a friendly number then fix it

• Each Slide has a string of problems that lead students to using a specific strategy. The last problem on each slide will be the one you use for the number talk.
• The sequence of problems allows students to apply the strategies from previous problems to subsequent problems or provides opportunities for students to reason with the same quantity from multiple perspectives.
• Choose a set of problems in one of two ways:
• Select a set of problems at random from each category; or
• Navigate in a systematic order by selecting problems with smaller numbers from a specific category, then building to larger numbers.
• When showing addition and subtraction problems, write them horizontally so that students are not constrained by algorithms.
• As each problem is shown, ask students, “What is the answer? How do you know?”

Multiply by a friendly number then fix it

Students adjust one number to change the number of groups. Then an adjustment is made to get the final product.

Category 1

The following number talks consist of 1 x 2-digit problems and have a connection to U.S. coin values. The problems in each section are purposefully ordered to help students build their knowledge from one problem to the next.

Category 1: String A

2 x 25

4 x 25

6 x 25

​

Category 1: String B

2 x 50

4 x 50

8 x 50

​

Category 1: String C

3 x 5

3 x 10

3 x 9

​

Category 1: String D

7 x 5

7 x 10

7 x 9

​

Category 1: String E

5 x 5

5 x 10

5 x 20

5 x 19

Category 1: String F

2 x 5

2 x 10

2 x 20

2 x 19

Category 1: String G

2 x 25

4 x 20

2 x 50

4 x 50

Category 1: String H

5 x 5

5 x 10

5 x 30

5 x 29

Category 1: String I

4 x 5

4 x 10

4 x 50

4 x 49

Category 2

The following number talks help students use relationships from the sequence to solve the final 1 x 3-digit problem.

Category 2: String A

4 x 25

4 x 200

4 x 250

4 x 249

Category 2: String B

6 x 20

6 x 100

6 x 120

6 x 119

Category 2: String C

3 x 50

3 x 100

3 x 149

​

Category 2: String D

3 x 10

3 x 50

3 x 100

3 x 149

​

Category 2: String E

6 x 50

6 x 300

6 x 349

​

Category 2: String F

4 x 60

5 x 300

4 x 359

​

Category 2: String G

3 x 100

3 x 200

3 x 199

​

Category 2: String H

5 x 100

5 x 300

5 x 60

5 x 359

Category 2: String I

8 x 50

8 x 100

8 x 200

8 x 199

Category 3

The following number talks help students use relationships from the sequence to solve the final 2 x 2-digit or 2 x 3-digit problem.

Category 3: String A

6 x 20

30 x 20

36 x 20

36 x 19

Category 3: String B

3 x 50

50 x 50

53 x 50

53 x 48

Category 3: String C

10 x 10

10 x 30

2 x 30

12 x 29

Category 3: String D

6 x 40

10 x 40

16 x 40

16 x 39

Category 3: String E

2 x 25

4 x 25

8 x 25

10 x 25

16 x 25

Category 3: String F

5 x 10

5 x 50

10 x 50

15 x 50

15 x 49

Category 3: String G

2 x 150

10 x 150

12 x 150

12 x 149

Category 3: String H

5 x 200

20 x 200

25 x 200

25 x 199

Category 3: String I

6 x 600

10 x 600

16 x 600

16 x 599