Addition and Subtraction

Writing Expressions

On the last page, we looked at some mathematical expressions. Expressions are useful, since they can help you keep track of the amounts you're adding.

Any addition problem can be turned into a written expression. For instance, say that you planned to have three friends come over for dinner. At the last minute, you invite two more. To get the total number of friends who are coming to your house, you might write an expression like this:

3 + 2 = __

The expression is just another way of describing the situation: three friends plus two more are coming over for dinner.

Now you try it. Write these situations as mathematical expressions. Don't solve the problems yet — simply set them up.

You ate three pieces of pizza for lunch. At dinner, you ate two more.

 
You already waited five minutes to see the doctor. The nurse tells you to wait five more minutes.

 

Your coat has four buttons on the right side and three buttons on the left side.