How to Play TwentyFour

The Goal

You are given four numbers. Combine all four of them, using addition, subtraction, multiplication and division, so the final result is exactly 24. Every number is used once, and you can use any operation as many times as you need.

Press New Game to get your first puzzle. Nothing starts until you press it.

Making a Move

• 1. Tap a numberIt is highlighted blue. Tap it again to let go.
• 2. Tap an operation+ − × ÷ The operation you choose is highlighted.
• 3. Tap a second numberThe two numbers merge into one result, which replaces the second number. For a subtraction or a division the number you tapped first comes first. The result stays highlighted, so for the next step you can go straight to an operation and a second number.

Keep going until one number is left. If it is 24, you have solved the puzzle.

Fractions

A step can produce a fraction, and fractions can be combined further. That is what makes the hardest puzzles hard. Fractions show as, for example, 8/3.

You cannot divide by zero. If you try, the board shakes and nothing changes.

The Buttons

• Undo and ResetUndo takes back your last move. Reset puts all four numbers back so you can start the puzzle again.
• HintHighlights the two numbers and the operation of the first step of a solution, from wherever you are now. It still counts as a solve. If you have gone down a path that cannot reach 24, it says so, and you can Undo or Reset.
• SkipGives you a new puzzle, after asking you to confirm. It has no effect on your streak.
• SolutionPlays out one way to make 24, step by step: the two numbers for each step light up, then fly into a line below the game, such as 4 + 7 = 11, and the result takes their place. The lines stay so you can follow the whole route. It ends the puzzle. You are asked first, because it counts as played and resets your streak.
• New GameStarts a fresh puzzle. If you are partway through one you are asked before it is abandoned. Whenever there is no puzzle running (when you first arrive, or after one ends) the button pulses and throws sparks to show it is your next step.

Game Options

• ModeChoose a mode below the board. In Whole numbers and Fractions allowed the numbers come from 1 to 13, like a deck of cards from ace to king. Whole numbers: every step must give a whole number, and the puzzles can be solved that way. Division is fine when it comes out even, like 12 ÷ 2 = 6, but a step such as 8 ÷ 3 is refused. Fractions allowed: any puzzle, and a step may give a fraction. Difficult: numbers from 1 to 30, and only puzzles that cannot be solved without a fractional step, such as 8, 8, 3, 3 or 1, 4, 5, 6. Changing the mode during a puzzle does not affect that puzzle; it applies to your next one. Every puzzle can be solved.

Stats and Streak

When logged in, every puzzle you finish is recorded: puzzles played, how many you solved, your solve percentage, your current streak and your best streak. Open Stats to see them. Each of the three modes keeps separate numbers.

Your streak is the number of puzzles you have solved in a row, with or without a hint. Using Solution resets it to zero. Skipping does not change it.