Addition and Subtraction
Introduction to Addition
What is Addition?
Addition is a way to put things together. When you add two amounts, you're counting them together, as one larger amount. Addition happens all the time in real life.
For instance, if this rabbit has babies...
For instance, if this rabbit has babies... she's adding to her family.
We can count the number of rabbits to find out how many there are.
We can count the number of rabbits to find out how many there are.
We can count the number of rabbits to find out how many there are.
We can count the number of rabbits to find out how many there are.
The total is 4. If you have 1 mother rabbit and 3 babies, you have 4 rabbits total.
What if there were four more rabbits?
As you can see, if you have 4 rabbits and add 4 more, you'll have 8 rabbits in total. You could write that like this:
4 + 4 = 8
4 + 4 = 8 is a mathematical expression. You could read it like this: four plus four equals eight. A mathematical expression is basically a math sentence. It uses numbers and symbols instead of words. When we write out expressions with addition, we use two symbols: + and =.
The plus sign (+) means that two things are being added together. This is why we put it between the rabbits — we had 4 rabbits and added 4 more.
The other symbol in our expression is the equals sign (=). When you see the equals sign in an expression, it means that two are more things are equal, or equivalent. Things that are equivalent don't always look or seem exactly alike, but they mean the same thing.
For instance, when you see someone you know, there's a few things you might say:
These words aren't exactly alike, but they mean the same thing. They're all ways to greet someone.
In math, the equals sign shows that two numbers or expressions mean the same thing, even though they might look different. Remember our rabbits? Since there were 8 rabbits total, we wrote 8 to the right of the equals sign.
See how each side means 8? 8 rabbits on the left, and the number 8 on the right. Both sides are equal.
Try it yourself — fill in the blanks to complete the equations.
