Lesson 20: Two-Digit Addition With Regrouping
Objective
Students will be able find the sum of two 2-digit numbers with regrouping.
Warm up
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Write this problem on the chalkboard: The class ran laps for 16 minutes and jumped rope for 19 minutes.
How many minutes of exercise did they get altogether?
Read the problem aloud as the students read it silently. Guide them to use MathLine to solve the
problem: 16 + 19 = ______ . Before students begin, have them move all of the rings on the
MathLine to the right side.
1. Add digits in the ones column. 6 + 9 = 15
tens ones
1
+
1
6
1
9
3
5
2. Regroup 10 ones into 1 ten. 15 = 1 ten & 5 ones
1 ten
5 ones
3. Record 5 in the ones column. Record a small 1 above the tens
column to show one ten regrouped from ten ones.
4. Add digits in the tens column. 1 + 1 + 1 = 3
1 ten
1 ten
1 ten
5. Write a 3 in the tens column
6. 16 + 19 = 35
The class exercised for 35 minutes altogether.
Student Page
Read the Practice section aloud as students read it silently. Encourage them to model the problem using
their MathLines. Have them complete the other activities independently.
Test Preparation
Have students work in pairs. Have one student write a 2-digit addition problem with regrouping.
Have the other student model it using MathLine. Switch roles.
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Answers on page 91
58
Name
Lesson 20: Two-Digit Addition with Regrouping
Practice
Find the sum: 18 + 15 =
1
+
1
1
8
5
3
3
8
+
5
1 Ten
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tens ones
3 Ones
1 ten
1 ten
1 ten
Activities
Use MathLine to solve the problems.
1.
tens ones
1
+
6
1
7
4
3
tens ones
4.
+
1
9
1
9
tens ones
7.
+
59
2
2
7
2
9
2.
tens ones
+
1
6
1
8
tens ones
5.
+
2
8
1
7
tens ones
8.
+
1
4
3
8
3.
tens ones
+
1
8
1
5
tens ones
6.
+
1
8
1
8
tens ones
9.
+
3
5
4
9
Name
(activities continued)
tens ones
10.
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+
6
2
7
8
tens ones
13.
+
16.
5
3
+
1
1
5
5
1
1
+
12.
6
8
3
2
+
17.
15.
4
9
+
3
4
18.
6
6
9
2
tens ones
5
2
+
tens ones
5
1
tens ones
+
tens ones
14.
3
7
tens ones
tens ones
11.
4
9
tens ones
+
2
1
7
7
Challenge
Circle two numbers to equal each sum.
1.) Sum of 48
29
17
19
35
2.) Sum of 62
48
21
38
14
3.) Sum of 53
22
16
37
23
4.) Sum of 66
27
29
39
24
60