Addition and Subtraction

What is Subtraction?

Subtraction is taking things away. When you have an amount and you subtract from it, the amount becomes smaller. Subtraction happens a lot in real life. 

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  For instance, imagine we have 8 eggs...

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  For instance, imagine we have 8 eggs...and we use a few. We're subtracting from the eggs we started with.

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  We can count the number of eggs to find out how many are left.

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  We can count the number of eggs to find out how many are left.

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  We can count the number of eggs to find out how many are left.

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  We can count the number of eggs to find out how many are left.

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  We can count the number of eggs to find out how many are left.

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  We can count the number of eggs to find out how many are left.

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  Five eggs are left. If you start with eight eggs and use three of them, then five eggs are left.

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As we saw, if you have 8 eggs and subtract 3 of them, you'll have 5 eggs left. In other words:

8 - 3 = 5

8 - 3 = 5 is a mathematical expression. You could read it like this: five minus three equals two. As we learned in Lesson 1, a mathematical expression is basically a math sentence that uses numbers and symbols. When we write a subtraction expression, we use two symbols: - and =.

The minus sign (-) means one thing is being subtracted from another. This is why we put it after the first group of eggs — we had 8 eggs and subtracted 5 of them.

Try using the minus sign! Fill in the blanks in the expressions below.

The Equals Sign

The other symbol in our expression is the equals sign (=). As we learned in Lesson 1, the equals sign means two numbers or expressions are equivalent, or equal. Even though they might look different, they mean the same thing.

In our eggs example, since 3 eggs were left, we wrote 3 to the right of the equals sign. That shows each side means 3. 3 eggs on the left, and the number 3 on the right. Both sides are equal.