Addition - the basics

Addition is when we find the total of two or more numbers.  We can use counting to add two single digit numbers.

Let's imagine that a bookshop sells 3 books in the morning, and then sells 2 books in the afternoon.

If the owner wanted to find out how many books she had sold in total then she could count them up:

1... 2... 3...    from the morning's sales

4... 5...          from the afternoon's sales

Therefore, she sold 5 books over the course of the day.  What the bookshop owner has done is to add up 3 and 2.

3 + 2 = 5

We can use our fingers to add up single digit numbers.

3 fingers (well, a thumb and two fingers) represents the first three books.  Then put up another finger for the first book from the afternoon, and another for the second book from the afternoon.

Adding up is a very important skill.  You'll do lots of adding up as you do more and more maths.

Place value

When we write a number with more than one digit, each of those digits has a different value, depending on its position.  We call this "place value".

 

H, T and U mean "Hundreds", "Tens" and "Units".  Because the 2 is in the hundreds position here it's not just two, it's actually two hundred.  This is very important, because without place value we could never make numbers that are bigger than 9.

We can split this number up into its parts like this:

We can use place value to help us to convert numbers from digits to words and from words to digits.  For instance, take the number "three hundred and nine".  From the words we know that there is a 3 in the hundreds column, and another 9 units:

There's a zero (0) in the tens column because it wasn't mentioned in the words.

When we start to add, multiply, subtract and divide large numbers, place value becomes even more important, so keep that in mind.

See if you can convert these numbers into words:

207
720
217

And see if you can convert these numbers into digits:

four hundred and ten
seventy-two
one hundred and fifteen