Adding and Subtracting on an Open Number Line within 20

This video tutorial teaches how to add and subtract numbers within 20 using an open number line. It covers the basics of addition and subtraction, explains the commutative property, and provides practical examples of using a number line for these operations. The tutorial emphasizes that while addition is commutative, subtraction is not, and demonstrates this through examples.

What does the commutative property of addition state?

• Numbers can be subtracted in any order to get the same difference.

• Addition and subtraction are the same operations.

• Numbers can be added in any order to get the same sum.

• Numbers can be multiplied in any order to get the same product.

How do you add numbers using an open number line?

• By counting back from the larger number.

• By counting back from the smaller number.

• By counting on from the smaller number.

• By counting on from the larger number.

What is the result of adding 9 and 7 using an open number line?

• 14

• 15

• 16

• 17

Why is subtraction not considered commutative?

• Because the order of numbers affects the result in subtraction.

• Because subtraction results in the same number regardless of order.

• Because subtraction is the same as addition.

• Because subtraction can be done in any order.

What is the result of subtracting 14 and 6 using an open number line?

• 6

• 8

• 10

• 12