How to Play

Goal

Work your mental math magic to find equations hidden among nine number cards. Keep what you find and collect the most cards to win!

Cards

There are 100 cards in the deck, each with a single number on it between 0 and 100. For optimal fun, certain cards appear more than once, like the mental-math-friendly single digits. Others, like the more reclusive primes, don’t appear at all.

Setup

One player volunteers to be the dealer, shuffles the deck, and then places nine cards face up as a 3-by-3 grid in the center of the table.

Since the game is a little harder for the dealer, you could try having all players be dealers at the same time, with each holding on to a portion of the deck and taking turns flipping new cards over.

Game Play

At the same time, all players (including the dealer) study the cards in the grid and try to create an equation using at least three cards and as many math symbols as needed. For example, the cards 2, 4, 7, and 1 above could be arranged to make 2 + 4 = 7 - 1.

Only addition (+), subtraction (-), multiplication (x), division (÷), and square roots (√) are allowed, but they can be used in any way necessary! Players can add as many of these symbols (plus parentheses) in any order needed to make the math work. However, each number card can only be used once in a given equation, and numbers not on cards in the grid cannot be used at all.

When a player finds an equation, she shouts the result, such as “Six!”, which immediately locks out all other players and gives her a chance to prove that the math works. If the proof checks out, she takes the three or more cards that were involved and keeps them in front of her.

Remember to shout the resulting number of the equation rather than anything like “Got it!” or “Found one!”. If you don’t shout the number, you don’t get your lockout and someone else can jump in!

Players should be careful not to shout a number unless they’re ready with a proof! If their math is invalid, if their proof’s result is different than the number they shouted, or if they take more than about 10 seconds while showing their proof, they lose their lockout and have to wait 10 more seconds before they can try again.

Every time an equation is found, the dealer replaces the cards that were taken with n ew ones so that there are always nine cards face up in the center of the table. If at any point before the deck runs out players are stumped and can’t find any more equations, the dealer can add 3 more cards to the table.

If you find an equation while the dealer is dealing, that’s OK! Shout the result as usual, stop the dealer from dealing, and proceed to show your proof as usual.

Players continue finding equations until all the cards in the deck are used up and no more equations can be found.

Winning

Once all the cards in the deck are gone and no more equations can be made, the game is over and players count up their points. Each card is worth 1 point and the player with the most points wins!

EXAMPLE

Let's imagine we're playing with these 9 cards. Here are some examples of equations that can Example tick and can't Example cross be made...

Example cards circle
Used in Equation
Result
Proof
Used in Equation
Result
Example tick
Addition
Shouted result 01
Card proof left 01=Card proof right 01
Example tick
Addition
Card proof left 01=Card proof right 01
Shouted result 01
Example tick
Subtraction
Shouted result 02
Card proof left 02=Card proof right 02
Example tick
Subtraction
Card proof left 02=Card proof right 02
Shouted result 02
Example tick
Multiplication
Shouted result 03
Card proof left 03=Card proof right 03
Example tick
Multiplication
Card proof left 03=Card proof right 03
Shouted result 03
Example tick
Division
Shouted result 04
Card proof left 04=Card proof right 04
Example tick
Division
Card proof left 04=Card proof right 04
Shouted result 04
Example tick
Fractions
Shouted result 05
Card proof left 05=Card proof right 05
Example tick
Fractions
Card proof left 05=Card proof right 05
Shouted result 05
Example tick
Parentheses
Shouted result 06
Card proof left 06=Card proof right 06
Example tick
Parentheses
Card proof left 06=Card proof right 06
Shouted result 06
Example tick
Square Roots
Shouted result 07
Card proof left 07=Card proof right 07
Example tick
Square Roots
Card proof left 07=Card proof right 07
Shouted result 07
Example tick
Negatives
Shouted result 08
Card proof left 08=Card proof right 08
Example tick
Negatives
Card proof left 08=Card proof right 08
Shouted result 08
Example tick
Zeros
Shouted result 09
Card proof left 09=Card proof right 09
Example tick
Zeros
Card proof left 09=Card proof right 09
Shouted result 09
Example tick
Multiple Equals
Shouted result 10
Card proof left 10=Card proof center 10=Card proof right 10
Example tick
Multiple Equals
Card proof left 10=Card proof center 10=Card proof right 10
Shouted result 10
Example cross
Less Than 3 Cards
Shouted result 11
Card proof left 11=Card proof right 11
Example cross
Less Than 3 Cards
Card proof left 11=Card proof right 11
Shouted result 11
Example cross
Exponents
Shouted result 12
Card proof left 12=Card proof right 12
Example cross
Exponents
Card proof left 12=Card proof right 12
Shouted result 12
Example cross
Other Numbers
Shouted result 13
Card proof left 13=Card proof right 13
Example cross
Other Numbers
Card proof left 13=Card proof right 13
Shouted result 13
Example cross
Duplicates
Shouted result 14
Card proof left 14=Card proof right 14
Example cross
Duplicates
Card proof left 14=Card proof right 14
Shouted result 14
Example cross
Wrong Result
Shouted result 15
Card proof left 15=Card proof right 15
Example cross
Wrong Result
Card proof left 15=Card proof right 15
Shouted result 15

MORE WAYS TO PLAY

Proof! Solitaire

Take that mental math magic to the next level with this solo challenge! It plays exactly like the classic game, but the lone dealer now times himself to see how quickly he can make it through the deck on his own. Getting a seriously fast time earns some serious bragging rights.

Proof! for Kids

Some younger players may be advanced enough to rival even adults, but small modifications may be needed for others to make the game more accessible and fun. Depending on players’ skill levels, try one or more of the following:

  • Play without square roots
  • Play with numbers only up to 30 or 50
  • Play with 12 cards out on the table rather than 9

When playing without any adults, the young dealer may also enjoy sitting out of the game and acting as a moderator, getting to decide who shouted what number first and making sure everyone’s math checks out.

TRY THE
WEEKLY CHALLENGE
MATH PUZZLES!

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Jumpstart your brain every Monday when we post a new set of nine cards that hides a challenging equation. Can you find the proof?

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