©Curriculum Associates, LLC Copying is not permitted. 21Lesson 3 Understand Mental Math Strategies (Make a Ten)
Name:
How does thinking about number paths help you add and subtract in your head?
Study the example showing the make a ten strategy on a number path. Then solve Problems 1–6.
1 Make a ten to add 9 1 6 First write all the number partners of 6
2 Make a ten Fill in the missing numbers
9 1 6 5 ?
9 1 5 10 and 10 1 5
So, 9 1 6 5
Example
Add 8 1 5
Think of a number path Start at 8 Add 2 to make 10
You need to add 3 more
5 5 2 1 3
So, 8 1 5 5 13
Lesson 3
Understand Mental Math Strategies (Make a Ten)
7 8 9 10 11 12 13
2 3
9 10 11 12 13 14 15
©Curriculum Associates, LLC Copying is not permitted.22 Lesson 3 Understand Mental Math Strategies (Make a Ten)
Solve.
3 Subtract Fill in the missing numbers
11 2 4 5 ?
4 5 3 1 1
So, 11 2 4 5
4 Use 2 and 2 for the number partners instead in Problem 3 What is different?
5 Subtract Fill in the missing numbers
14 2 8 5 ?
8 5 1
So, 14 2 8 5
6 How is making a ten to add the same as making a ten to subtract? How is it different?
6 7 8 9 10 11 12
65 7 8 9 10 11 12 13 14
©Curriculum Associates, LLC Copying is not permitted. 23Lesson 3 Understand Mental Math Strategies (Make a Ten)
Name:
Explore the Make a Ten Strategy
Study how the example shows making a ten to add. Then solve Problems 1–6.
1 Fill in the missing numbers to find 9 1 4
9 1 4 5 ?
9 1 1
So, 9 1 4 5
2 Look at the open number line in Problem 1 How would you change the numbers to show 9 1 5?
Example
8 1 7 5 ?
8 1 2 1 ?
The partners 8 and 2 make 10
8 1 7 5 ?
8 1 2 1 5
Add 5, the other partner of 7
So, 8 1 7 5 15
Lesson 3
8 10
2
8 10 15
2 5
9 10
©Curriculum Associates, LLC Copying is not permitted.24 Lesson 3 Understand Mental Math Strategies (Make a Ten)
Solve.
3 Make a ten to subtract Fill in the missing numbers to show 12 2 4 5 8
4 Complete the number sentences
12 2 5 10 16 2 5 10
13 2 5 10 15 2 5 10
5 Fill in the missing numbers to find 15 2 9
15 2 9 5 ?
15 2 9 5
6 Jan circled the problems that she cannot solve in her head by making a ten
14 2 7 8 2 2 12 2 8 9 2 4 15 2 6
Look at all of the problems Why doesn’t Jan make a ten to solve the circled problems?
8 10 12
10 15
©Curriculum Associates, LLC Copying is not permitted. 25Lesson 3 Understand Mental Math Strategies (Make a Ten)
Name:
Reason and Write
Look at the example. Underline a part that you think makes it a good answer.
Example
1 Write an addition sentence you can solve by making a ten
2 Describe the steps for making a ten to add Write three or four steps You can use words and pictures
1 5
Step 1 Start at 8. Add a number to 8 to make 10. The number to add is 2. 8 1 2 5 10.
Step 2 Use 2 as a partner. Find the other partner that makes 6. The partners are 2 and 4.
Step 3 Think of moving 2 places on a number line from 8 to 10. Then move 4 more places from 10 to 14.
8 10 14
2 4
Step 4 The number you end at is your answer. It is 14.
Lesson 3
8 6 14Where does the example . . .• show the
addition sentence?
• use words to explain?
• use numbers to explain?
• use a picture to explain?
©Curriculum Associates, LLC Copying is not permitted.26 Lesson 3 Understand Mental Math Strategies (Make a Ten)
Solve the problem. Use what you learned from the example.
1 Write a subtraction sentence you can solve by making a ten
2 Describe the steps for making a ten to subtract Write three or four steps You can use words and pictures
Show your work. Did you . . .• show the
addition sentence?
• use words to explain?
• use numbers to explain?
• use a picture to explain?