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Subtraction with Help from the Number Line


Subtraction and minus are two names for the same mathematical operation. Subtracting positive numbers from each other makes things smaller, and moves you towards the left on the number line.

Rule

Important Words and Expressions

When you are talking about subtraction, all the numbers you are subtracting from each other are called terms. When you subtract several terms from each other, the answer is called a difference.

TERM TERM = DIFFERENCE

It’s important to remember these names for different parts of a subtraction, so you should memorize them!

Remember that you can always use the number line to help you with subtraction. The number of jumps to the left you need to get the answer is equal to the number you are subtracting.

Example 1

Find 13 6 = 7

In this case, 13 and 6 are our terms, and 7 is their difference.

6 jumps on the number line, starting at 13 and ending at 7

Think About This

What do you think will happen when you try to subtract 0 from another number?

Absolutely nothing!

10 0 = 10100 0 = 10042 0 = 42

This is because you are jumping 0 steps to the left on the number line, so the number isn’t getting any smaller. Subtracting 0 is the same as removing nothing.

Example 2

Find 48 25 = 23

In this case, 48 and 25 are our terms, and 23 is their difference.

25 jumps on the number line, starting at 48 and ending at 23

Example 3

Find 67 24 = 43

In this case, 67 and 24 are our terms, and 43 is our difference.

You can use the number line to find this. The number you are subtracting shows how many jumps to the left you need, which in this case is 24.

Remember: Friends of 10 are pairs of numbers that sum to 10.

Think About This

What happens if you subtract a friend of 10 from 10?

Because the friends of 10 are the numbers that become 10 when you add them together, the difference between 10 and one friend would be the other friend of 10. 10 1 = 9 10 8 = 2 10 3 = 7 10 6 = 4 10 5 = 5

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Addition and Subtraction (The Place-value System)