Little N., who is 4.5yo, can count from 1 to 100, she understands the value of the numbers (like 10 is less than 100), she also knows the names of 100s (one hundred, two hundred, etc); what she can't do is count by 1 from 100 on (101-102-103, etc) or to name the 3-digit numbers (123 is not called "one-two-three"). So, to help her learn that I've made a home version of Montessori Decimal Cards. You can buy them for $20 plus shipping, but the fact is, that for many activities you need more than one set, and then it becomes too expensive.
Sturdy Board. You can also either glue the print-out onto the card stock, or laminate it.
Before you begin, make sure that your child can name all the 100s, 10s and single digit numbers. Or use the cards to teach her what they are called. This is a first step. You can use the decimal cards in many ways, but I'll only tell you about one "game" today. It's primary purpose it to help the child figure out the concept of naming 3-digit numbers.
He's how you do it. First, show the cards to the child. Ask her to name them. Start with ones, then do tens and hundreds. If she gets bored quickly, then randomly draw some cards out and ask her to name them.
Next tell her that you are going to make some numbers and learn how to name them. The numbers on the cards are color coded (all the 100s are red for example, and 10s are blue). Take one of the 10s card [50, e.g.], put it down and say . Then take a single digit one [4 e.g], put it on top of the 10s card so it covers the 0 [say "4"]. Say . Now ask your child to make and name a 2-digit number.
Now do the same thing but using the 100s, 10s and 1s. If your child says 2 instead of 200, take the top cards off and show her the bottom card. Say: "this card is called 200, not 2. You should say the name of this card". Do groups of numbers like 101, 110 and 111 (pattern wise). Note that the numbers like 213, 314 (the ones that have teens in them) might be more difficult to decode.
Don't forget to praise your child's efforts. Practice this game a few times, and you'll be amazed how quick she'll learn it.
The video of little N. calling out the numbers is coming soon. And also the template so you could make your own set.