Adding Two 2-Digit Numbers by Making 10s

This lesson teaches how to add two-digit numbers vertically by decomposing numbers. It explains the concept of decomposition, the commutative property of addition, and provides examples using crayons and bees to illustrate the process. The lesson concludes with a summary of the key points covered.

What does the commutative property of addition state?

• The sum is always less than the addends.

• The sum is always greater than the addends.

• The sum remains the same regardless of the order of addends.

• The sum changes when the order of addends is changed.

How can the number 23 be decomposed?

• Into 15 and 8

• Into 2 and 3

• Into 20 and 3

• Into 10 and 13

When adding 36 and 44 vertically, what is the sum of the ones place?

• 11

• 10

• 9

• 8

In the example of adding 36 and 44, what is the total sum?

• 90

• 100

• 70

• 80

What is the final sum when adding 49 and 23 using vertical addition?

• 62

• 72

• 82

• 92