Save Twenty

Materials: Five Dice per game; scratch paper and pencil
Topics: Addition, estimation, probability
Recommended Grades: 1, 2, 3
Common Core: 1.OA.C.5, 1.OA.C.6, 2.OA.B.2

A quick, fun game for arithmetic practice with numbers up to 20.

The game is quick and fun, with an element of risk that makes each turn exciting.
Lots of estimation and addition practice are built into every game.

Choose a volunteer and demonstrate the game where everyone can see it.
Once you have played through a few rounds with the volunteer, have students play the game in pairs or groups or three.

Play is best with 2 or 3 players.
The goal of the game is to roll as close to (or equal) to 20, without going over.
You’ll have four rounds per turn.
For the first rounds, roll all five dice. You may save as many as you like, from zero to all.
Any dice that are saved may not be re-rolled for the rest of your turn.
For your second and third round, roll the dice you haven’t saved. You may save as many of these as you like.
For the fourth and final round, roll any remaining unsaved dice.

Now score your points. If your five dice form a sum greater than 20, you score 0.
If the dice sum to 20 or less, that number is your score for the turn.
Play for 9 turns. The winner is whoever has the greatest score at the end of the game.

Example Game

• On my turn, I roll 2, 2, 3, 5, 6 in round 1. I save 3 and 5, and reroll the other dice.
• In round 2, I reroll the three unsaved dice, and get 1, 1, 6. I don’t save any of these dice.
• On round 3, I reroll the three unsaved dice, and get 2, 5 and 6. I save 2 and 5.
• On round 4, I reroll the only unsaved die and roll a 1.
• My score for this turn is 3 + 5 + 2 + 5 + 1 = 16. Because I didn’t go over 20, my score for this turn is 16.
• When my turn is over, I pass along my dice, and the next player goes.

• Is there a “best” strategy for this Save Twenty? Are any strategies better or worse than each other?
• If you roll 18 on your first turn, should you take the 18 points, or keep trying to do better.
• If 20 is the best number to get to by round 4 using 5 dice, What’s the best number to try to get to by round 3 using 4 dice?

This wonderfully simple game is quick to learn and fun to play.
Perfect for helping students develop their number sense for numbers under 20.
Deeper probability questions lurk in the background.

• Save Twenty is straightforward to use in the classroom.
  Once students know how to play, you can make it available for them as an option during free time/choice time.
• Foam dice is a good option to prevent noisy dice rolls.
• Make a class rule that if the dice roll of the table, it’s a re-roll.
  If dice are flying too far, you can also make a class rule that if the dice roll off the table it counts as a lost turn.