Page 46 - TG_G1_CH6_CHRIS

Adding Two-Digit Numbers with
Regrouping
Hand out cubes and have children divide each cell in the place value chart
• Place 18 cubes on the place-value chart. Make 1 tower of 10 cubes in the
tens place and 8 single cubes in the ones place. Add 5 more cubes to the into halves. In the first half, place 18 cubes so there is 1 tower of 10 in the tens
ones place. place and 8 single cubes in one’s place.
• Rearrange the cubes to make 2 towers of ten cubes in the tens place and
the rest in the ones place.
Say: Now, Add 5 more cubes in the one’s place,
Can you rearrange the two places in the other half to make each 10 cubes in
Tens Ones ones as one tower in tens place and the rest in ones?
How many cubes are in the ones place of 18? 8
How many cubes are in the ones place after rearranging 5 cubes with the 8
cubes? 3

Write an addition sentence. 18 + 5 = 23

ANCHOR ACTIVITY

1.NBT.4 Add within 100, including adding a two-digit number and a one-digit number, and adding a two-digit number and a multiple of
10, using concrete models or drawings and strategies based on place value, properties of operations, and/or the relationship
between addition and subtraction, relate the strategy to a written method and explain the reasoning used. Understand that in
adding two-digit numbers, one adds tens and tens, ones and ones, and sometimes it is necessary to compose a ten. Use the Anchor Activity for this lesson as a warm-up to gauge
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children’s prior knowledge and help them engage at the
beginning of class.

TIME TO LEARN
TIME TO LEARN

Ones
Tens
+ + Tens Ones
2
2 +1+1 5 5 To add Have children model both 25 and 7 using cubes. Ask: How many base ten rods
To add
+ + 7 7 25 + 7. Regroup do you have? 2. How many unit cubes do you have? 12.
25 + 7, regroup
3 3 2 2 10 ones as 1 ten.
10 ones as 1 ten.
+ + Direct them that they can model the 12 as 1 base ten rod and 2 unit cubes.
25 + 7 = 32
25 + 7 = 32
Ask: How many base-ten rods do you have in all? 3
How many unit cubes do you have? 2. What is the sum of 25 and 7? 32
+ + = 32
= 32
Direct children’s attention that they can use place value chart in adding two
regroup digit numbers ensure that they know that usually they start adding from ones
STEP Add. place. Ask: What is 5 + 7? 12, Can we write the 12 in the ones place in? No
Add.
BY
STEP
Tens
Ones
Tens Ones Direct children that we will write only the 2 on the ones place. While the 1 is
4 4 +1 +1 4 4 actually 1 ten, so it will be written above the 2 in the tens place. Ask: What you
44 + 6 =
1 1 44 + 6 = 50 + + 6 6
5 5 0 0 will write in the tens place? 3 Ensure that children add the 1 with the 2 in the
tens place. Direct children’s attention to the meaning of regrouping and that
Ones
Tens
Tens Ones
8 8 7 7 moving digit from the ones place to the tens place then adding it to the tens
87 + 9 =
2 2 87 + 9 = 96 + + 9 9 place is called regrouping. Let children solve 38 + 4 independently to ensure
9 6 they masters the concept of adding with regrouping.
Tens Ones
Tens
Ones
5 5 6 6
56 + 6 = 62
3 3 56 + 6 = + + 6 6
Common
6 2 Common
Errors
Errors
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When adding the ones of two numbers together children may forget to
add the regrouped tens to the sum.
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