Rules & objective
Use all four cards exactly once to make 24.
- Use every card exactly once. Two cards with the same value are still separate cards and must each be used.
- Parentheses control grouping. Multiplication and division take priority over addition and subtraction when parentheses do not override them.
- Fractional intermediate values are allowed. Dividing by zero or building an incomplete expression will not produce a valid answer.
Key terms
- Expression
- The complete calculation built from cards and operation buttons.
- Intermediate value
- A result created before the whole expression is evaluated.
- Grouping
- Using parentheses to determine which calculation happens first.
Difficulty levels
| Level | What changes |
|---|---|
| Easy | Six approachable card sets with whole-number solutions. |
| Medium | Six multi-step card sets. Parentheses and division can help. |
| Hard | Six card sets that require a fractional intermediate result. |
Changing difficulty starts a fresh round. Personal bests are tracked separately.
This version on puzzle free online
Each tier contains six card sets. Hard sets require a fractional intermediate result. Hint reveals one solution; a result completed after using Hint is not saved as a personal record.
Common questions
May I join two cards into a two-digit number?
No. Use the supplied arithmetic operations between cards; concatenation is not an allowed operation.
How do I reuse a card after changing my mind?
Undo removes the last expression token. Once that card token is removed, the card becomes available again. Clear removes the whole expression.