Adding 2-Digit Numbers by Making 10s

This video tutorial teaches how to add up to four 2-digit numbers by making 10s. It begins with a review of making 10s and skip counting by 10s. The lesson includes examples of calculating costs for lunch, movie expenses, and bowling alley costs, demonstrating how grouping numbers to make 10 simplifies addition. The tutorial also clarifies that numbers can be added in any order without affecting the sum, emphasizing the commutative property of addition.

What is a friendly number, and why is it useful in addition?

• A number that is easy to multiply

• A number that is easy to divide

• A number that ends in zero, making it easier to add

• A number that is a prime number

Which of the following pairs of numbers add up to ten?

• 6 + 3

• 4 + 5

• 3 + 7

• 2 + 9

In the meal cost example, which two numbers were grouped first to make ten?

• 5 and 3

• 4 and 6

• 3 and 7

• 5 and 5

How much did the total cost of the trip to the movies amount to?

• $20

• $30

• $23

• $25

What was the total cost at the bowling alley?

• $35

• $32

• $40

• $30