Tens and ones

You know how to count to 10. Watch what happens after that — the numbers from 11 to 20 are clever. Each one is just a ten with a few more added on top.

A bag of ten

Imagine you have ten little marbles. You put them in a bag and tie it up. From now on, this bag is "one ten".

If you put two more marbles next to the bag, how many marbles do you have? One bag of ten plus two more — twelve. We write 12.

Reading two-digit numbers

When you see 14, look at it like this:

the first digit (1) is the number of tens — one ten,

the second digit (4) is the number of ones — four extra marbles.

So 14 means one ten and four ones. Together: ten and four — fourteen.

Try a few

• 11 → one ten and 1 one
• 13 → one ten and 3 ones
• 17 → one ten and 7 ones
• 20 → two tens and 0 ones (two full bags!)

Why two bags is twenty

Twenty is special. Two bags of ten = 20. Once you have two full bags, you have moved on to a brand-new place — twenty. After 20 you start again with 21, 22, and so on.

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