Page 40 - TG_G1_CH6_CHRIS

Adding a Two-Digit Number
and a Multiple of 10
Say: Circle the numbers that when added together give the sum.
• Circle the numbers that when added together give the sum.
• The first one is done for you.
Ask: Is 5 + 10 = 15? Yes
Say: Since it is correct, circle the three numbers.
20 5 3 40 43 6 Ask: Would you circle 40, 60, and 34? No
What about 40, 60 and 34, would you circle them? No
2 10 50 60 5 9

22 15 12 34 5 39
ANCHOR ACTIVITY
40 30 34 26 11 70

30 30 42 2 40 60 Use the Anchor Activity for this lesson as a warm-up to gauge
children’s prior knowledge and help them engage at the
70 60 29 28 1 10 beginning of class.

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.
289

TIME TO LEARN
TIME TO LEARN
TIME TO LEARN
Tens Ones
4 0
+ 2 8 Recall that in order to add two-digits addends, we can either model or use
6 8 a place-value chart. Remind children that when modeling addends using
40 + 28 = 68 base-ten blocks and cubes, they count cubes together and base-ten blocks
2-digit number together to find the sum.
STEP multiple of 10
BY Add.
STEP Ensure that children know that base-ten rods usually represent tens and cubes
usually represent ones. Provide children with an empty place chart and direct
1 Tens Ones
3 5 them to write 40 and 28 in their correct place in the chart. Ask: When adding
+ 2 0 two-digit numbers, do you start with the ones or tens place? Ones
35 + 20 = 55 5 5
What is the sum of 40 and 28? 68
2 Tens Ones
3 0
+ 4 2 To ensure that children master the concept of adding two-digit numbers, let
30 + 42 = 72 7 2 them find the sum of 72 + 20 independently.

3 Tens Ones
5 3
+ 1 0
Common
53 + 10 = 63 6 3 Common
Errors
Errors
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Children may add the tens only and forget to write down the ones.

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