Our seven year old created a card game with poker chips.  I enjoy playing it with him because he is using so much mental math.

He deals 5 cards to each person for the first hand (but only 3 cards to each on subsequent hands).  You can match 2 or more cards into either sets or runs. We turn in our matches to the banker, he calculates our score and he awards the chips, then the next hand is dealt.

Each card is worth 10 times its number value.  Aces are worth 200 points and face cards are worth 100. If you can get '4 of a kind', the value is doubled.  You are not required to turn in a match if you have one.

We use 3 colors of chips with the value of 10, 100, and 1000 points.  We play until someone reaches 5000 points.