Page 28 - TG_G1_CH6_CHRIS

Add Tens

• Place 20 red beads in the first box. Provide children with red and blue beads and two boxes.
• Place 30 blue beads in the second box. Say: Place 20 red beads in the first box and 30 blue beads in the second box.
• How many beads are there in the two boxes?
• Write the missing numbers and solve the addition sentence.
Ask: How many tens are in the first box? 2
How many beads are in the second box? 30
Box of red beads Box of blue beads How many beads are in the two boxes altogether? 50
How many tens are there? 5

Complete the addition sentence.
2 tens + 3 tens = 5 tens, 20 + 30 = 50

2 tens + 3 tens = 5 tens
ANCHOR ACTIVITY
20 + 30 = 50

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 Use the Anchor Activity for this lesson as a warm-up to gauge
adding two-digit numbers, one adds tens and tens, ones and ones, and sometimes it is necessary to compose a ten.
281 children’s prior knowledge and help them engage at the
beginning of class.

TIME TO LEARN TIME TO LEARN
Tens Ones
5 0
+ 3 0
8 0 Recall the concept of counting on tens, and check that children can count on
5 tens + 3 tens = 8 tens in 10s to 120. Direct children that counting is related to adding and they can
50 + 30 = 80 use the basic facts of addition to make adding tens easier.
You already know
5 ones + 3 ones = 8 ones Write 50 + 30 = on the board. Discuss with children that 50 is the same as 5 tens
5 + 3 = 8
and 30 is the same as 3 tens.
Say: We can replace the 50 with 5 tens and the 30 with 3 tens.
STEP add tens
BY
STEP Add.
Write 5 tens + 3 tens.
Tens Ones
1 4 + 5 = 9 4 1 0 Ask: what is 5 + 3 equal to 2? 8
40 + 50 = 90 + 4 0 What is 5 tens + 3 tens? 8 tens
5 0
What is 50 + 30 equal to? 80
Tens Ones
2 3 + 3 = 6 5 2 0 Encourage children to solve 30 + 20 by finding it’s basic fact in order to ensure
+ 6 0 they have mastered the concept.
30 + 30 = 60
8 0
2 20
3 6 8 tens + 1 ten = 9 tens
+ 5 + 50
Common
7 70 + = 90 Common
10
80
Errors
Errors
282
Children may become confused when asked to complete the
equation: ___ + 3 tens = 50
20 tens

419