UnderTen for families and classrooms

Every turn of UnderTen is a small sum. Players add up their hand, compare totals and weigh the odds of the next card, and they do it because they want to win, not because it is homework. That makes it a good game for family card nights and for a maths lesson with a real deck of cards.

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The maths inside the game

Mental addition, every turn

A starting hand of seven cards adds up to about 46 on average. To know whether they can declare, players keep adding and re-adding their hand as it changes. Throwing a card means subtracting it. Taking one means adding it. After a few rounds, most players are doing this in their heads without thinking about it.

Number bonds to 10

The whole game is about getting below 10. Players quickly learn which small cards make 9 or less together, such as 4 + 3 + 2, or 5 + 2 + Ace + Ace. Picture cards are worth 10 each, so they also learn to see a King as "a whole ten".

Comparing and ordering

When someone declares, every hand is laid out and compared. Who is lowest? Is anyone equal? A tie matters, because the declarer must be strictly lowest to win. That is a natural way to talk about "less than" versus "less than or equal to".

Thinking about chance

Older players can start to reason about probability. Should I take the 3 I can see on the discard pile, or gamble on the deck? There are four of each rank in the deck: if two 7s have already been thrown, how likely is it that I draw another? Is a hand of 8 good enough to declare when there are five other players? Our numbers page and declare chart are good starting points for a discussion.

How to teach it in five minutes

1. Show the card values: Ace is 1, number cards are their number, Jack, Queen and King are 10.
2. Deal everyone 7 cards and let them add up their hand. It will be big, usually over 40.
3. Explain the turn: take one card, then throw one card. Matching cards, like two 5s, can be thrown together.
4. Explain the goal: when your hand is 9 or less at the start of your turn, you can say "Declare". Everyone shows their cards, and you win if nobody else is as low as you.
5. Play one round with cards face up so everyone can help each other. Then play for real.

The full rules, with an example round, are on the how to play page.

Easier house rules for beginners

These are house rules for learning. The online game always uses the standard rules.

• Open hands. Play with all cards face up so you can talk through each choice together. "Which card would make your hand smallest?"
• No ties lost. For a first game, let the declarer share the win on a tie, so it feels less harsh.
• Fewer picture cards. Take the Jacks, Queens and Kings out of the deck. Hands start smaller and get under 10 faster, which keeps first-time players interested.
• Single rounds. Skip the match to 50 and play one round at a time.

Once players are confident, put the picture cards back and try a full match. Adding each round's score to a running total is another bit of arithmetic practice in itself.

Classroom ideas

• Table groups of four. One deck per group of four players. A round takes a few minutes, so it fits at the end of a lesson.
• Score sheets. Have each group keep score to 50 on paper. Our real-cards page has a score sheet layout you can copy onto the board.
• Prediction questions. Before revealing hands after a declare, ask everyone to guess whether the declarer will win and to explain why.
• A probability experiment. Ask groups to deal 20 starting hands, add each one, and record the totals. Compare the class average with the expected value of about 46.
• Strategy writing. Older pupils can write their own top three tips and compare them with our strategy guide.

A note on the online game

Everything on this page works with an ordinary deck of cards, and that is how we suggest using UnderTen with children and in class. The online game at undertengame.com is a general audience game that is not directed at children under 13, and it shows ads between games. It has no free-text chat (players can only send a fixed set of stickers) and no accounts. Our privacy page explains what the site collects.