## Subjects

# The four basic arithmetical operations

Which expressions mean the same as addition?

## The four basic arithmetical operations

There you are! Second sheet done. Eight more cookies! And we already had one sheet with eight cookies. That makes it...

Eight plus eight, of course. Sixteen cookies. Yes. Sixteen cookies. You add eight to eight, and the result is sixteen.

This way of calculating is addition. You add. Reckon up. Total. Sum.

Another way of looking at it is to study The Number Line. When you add, you go to the right on the Number Line. If you have eight cookies to begin with, you start at the eight in The Number Line. If you add eight more cookies, move eight steps to the right, and land on... sixteen.

This is addition. The numbers you use to calculate are called terms, and the result is the sum. But hey, another sheet of cookies is ready. How many cookies are there now? 24.

Eight plus eight plus eight. You add some more. Plus. But there is another way of getting the answer. If you bake a sheet of eight cookies three times, you get the number of cookies by calculating three times eight.

This is multiplication. Do you see that there is a connection between addition and multiplication? Because multiplication is a repeated addition. 8+8+8 equals three times eight. If you bake ten sheets of cookies, the number of cookies can be described as a repeated addition … ...

or, more simply, as a multiplication. Ten times eight. These operations are connected. The numbers you use to calculate are factors, and the result is a product. Now, the guests start to arrive to the party.

There are six, and they have one cookie each. They had 24 cookies. Ate six of them. Then there are 24 minus six cookies left. Minus means remove, or subtract.

The operation is called subtraction. Let's look at the Number Line again. When you subtract, "take minus", you go to the left on The Number Line. Start at 24, go to the left six steps, one for each cookie eaten. You end up at 18.

When we subtract, we move to the left on the Number Line. When we add, we move to the right. This means that subtraction is addition backwards. This is the connection between plus and minus. They are opposites.

The numbers you calculate with when subtracting are called terms, just like in addition. The result is the difference. Difference is the size of the gap between two numbers. It can be understood this way. A pile consists of 24 cookies.

We mark six of them. The difference between 24 and 6 is -- 18. More guests arrive at the party. Now there are nine, and they want to share the cookies equally. That makes two cookies on each plate.

Because 18 divided by nine, is two. This is division. 'Divided by'. When you want to split a number into equally sized parts... You divide. The number at the top is the numerator.

The number at the bottom is the denominator and between them is a dividing line. The result is a quotient. Does division have any connection to the other operations? Yes. Division is multiplication backwards.

Watch! 18 divided by nine equals two. And two times nine is 18. Times and "divided by" are connected, and are each other's opposite. The four operations and their connections.

Remember. Addition. Plus. Subtraction. Minus.

This is addition backwards. Multiplication. Times. A repeated addition. And division.

Divided by. Multiplication backwards.