You already know all the numbers up to 20. Now we make the jump — all the way to 100. Don't worry, the trick is the same: every two-digit number is just a few full tens with some ones left over.
A road of bags
Imagine ten bags, each holding ten marbles. Put them in a row.
1 bag = 10
2 bags = 20
3 bags = 30
...
9 bags = 90
10 bags = 100
That is your road from 0 to 100. Every full bag adds another ten.
Two-digit numbers
When you see 47, look at it like this:
the first digit (4) is the number of full bags — four tens (40),
the second digit (7) is the loose marbles — seven ones.
