Exploring Compatible Numbers for Addition

The video tutorial explains the concept of compatible numbers, also known as friendly numbers, which typically end in zero or five. It distinguishes compatible numbers from rounding, emphasizing their utility in mental math. Through examples, the video demonstrates how to use compatible numbers to simplify addition problems, highlighting their closeness to exact numbers. The tutorial concludes by reinforcing the importance of recognizing compatible numbers for efficient mental calculations.

What are compatible numbers often referred to as?

• Rounded numbers

• Friendly numbers

• Exact numbers

• Decimal numbers

What is a key difference between compatible numbers and rounding?

• Compatible numbers can end in 5 or 0, while rounding always ends in 0.

• Rounding is used for subtraction, not addition.

• Compatible numbers are only used in multiplication.

• There is no difference; they are the same.

In the example 27 + 38, what compatible number is chosen for 27?

• 35

• 30

• 28

• 25

What was the compatible number used for 38 in the example 27 + 38?

• 38

• 35

• 40

• 45

What is the sum when using compatible numbers for 27 + 38?

• 65

• 66

• 70

• 75

In the example 75 + 86, which number is already considered a compatible number?

• 75

• 80

• 85

• 86

What compatible number is chosen for 86 in the example 75 + 86?

• 80

• 95

• 85

• 90

What is the sum when using compatible numbers for 75 + 86?

• 161

• 160

• 170

• 150

In the three-digit example, what compatible number is chosen for 143?

• 140

• 145

• 150

• 155

What is the final sum using compatible numbers for 143 + 761?

• 895

• 905

• 950

• 960