SIMCC Games · Teacher guide
Fifteen
Take turns picking numbers 1 to 9; the first to hold three that make 15 wins.
- Trains
- Adding three numbers to 15 · Number bonds · Blocking and planning ahead
- Ages
- 7 and up
- In class
- Pass and play. Pairs share one device. Choose Lower Division, where the sums helper is always on.
A ten-minute starter
- Show about 2 minWrite 1 to 9 on the board. Two players take turns to take a number. The first to hold three numbers that add up to exactly 15 wins. Play one quick game against the class.
- Play about 6 minPairs play pass and play at Lower Division. Player 1 always goes first, so swap seats after each game.
- Talk about 2 minAfter a game the result shows a magic square: 2 7 6, 9 5 1, 4 3 8. Every line adds up to 15. Ask: what game is Fifteen really?
Questions to ask the class
- You hold 2 and 6. Which tile makes 15?Listen for: 7. If the other player has it, that pair cannot win.
- You hold 7 and 8, which make 15. Why have you not won?Listen for: A win needs three tiles.
- Why is 5 a strong tile to take?Listen for: It is in four ways to make 15, more than any other tile: the centre of the magic square.
A common mistake
Watching only your own tiles and letting the other player finish 15.
How to help: Ask: which tile would finish their 15? The sums helper shows every pair a player holds and the third tile it needs. Hint (H) names the best tile and says why.
Assign it
On the coach dashboard, choose your class under Cohorts. In Assign practice, pick Fifteen and the drill Fifteen, add a due date if you want one, then press Assign. Students find it on their Train page.
It opens against the computer. Ask students to start at Lower Division.
Wins against the computer show under By game, as each student's device reported them. Pass-and-play games do not show.