Add Three and Four 2-digit Numbers by Making 10s

This lesson teaches how to add 3 to 4 two-digit numbers vertically by making tens. It reviews key concepts like decomposing numbers and the commutative property of addition. Through examples involving chocolate chip cookies, students learn to set up addition problems vertically, add ones and tens separately, and understand that the order of addends does not affect the sum. The lesson concludes with a summary of the vertical addition process.

What does the commutative property of addition state?

• Addition must be done horizontally.

• Addition is only possible with single-digit numbers.

• The order of addends changes the sum.

• The order of addends does not change the sum.

In the example of adding chocolate chips, what is the first step in the vertical addition process?

• Subtract the smaller number from the larger one.

• Multiply the numbers.

• Add the ones first.

• Add the tens first.

How many chips are there in total after adding 38, 27, and 12?

• 67

• 57

• 87

• 77

What is the total number of chips after Tavius adds 11 more chips?

• 78

• 88

• 98

• 108

When adding 38, 27, 12, and 11, what is the sum of the ones place before carrying over?

• 28

• 10

• 20

• 18