Krypto is a card game designed by Daniel Yovich in 1963 and published by Parker Brothers

Parker Brothers

Parker Brothers is a toy and game manufacturer and brand. Since 1883, the company has published more than 1,800 games; among their best known products are Monopoly, Cluedo , Sorry, Risk, Trivial Pursuit, Ouija, Aggravation, and Probe...

 and MPH Games Co.. It is a mathematical game that promotes proficiency with basic arithmetic

Arithmetic

Arithmetic or arithmetics is the oldest and most elementary branch of mathematics, used by almost everyone, for tasks ranging from simple day-to-day counting to advanced science and business calculations. It involves the study of quantity, especially as the result of combining numbers...

 operations. More detailed analysis of the game can raise more complex statistical questions.

The Krypto Deck and Home Rules

The Krypto deck consists of 56 cards: three each of numbers 1-6, 4 each of the numbers 7-10, two each of 11-17, one each of 18-25. Six cards are dealt: a common objective card at the top and five other cards below. Each player must use all five of the cards' numbers exactly once, using any combination of arithmetic

Arithmetic

Arithmetic or arithmetics is the oldest and most elementary branch of mathematics, used by almost everyone, for tasks ranging from simple day-to-day counting to advanced science and business calculations. It involves the study of quantity, especially as the result of combining numbers...

 operations (addition, subtraction, multiplication, and division), to form the objective card's number. The first player to come up with a correct formula is the winner.

Krypto International Tournament Rules

The official international rules for Krypto differ slightly from the house rules, and they involve a system of scorekeeping.

Five cards are dealt face up in the center of the game table. (Each player works with the same set of five cards, rather than a set exclusive to them.) Then a sixth card is dealt face up in the center of the table that becomes the Objective Card. Each player commences (mentally) to mathematically manipulate the numbers of each card so that the last solution equals the Objective Card number. Krypto International Rules specify the use of whole numbers only, using addition, subtraction, division, multiplication and/or any combination thereof ... fractions, negative numbers or square rooting are not permitted. Each of the five cards must be used once and only once. The first player to solve the problem declares "Krypto" and has 30 seconds to explain the answer. When a player
"Kryptos" and cannot relate the proper solution, a new hand is dealt and the hand is replayed. The player that errored receives a minus one point in the score box for that hand and is not eligible to play for a score for the replay of that hand.

Each hand must be solved within three minutes or a new hand is dealt.

Example of Play:
Cards: 2, 1, 2, 2, 3 = 24 (Objective Card)
2 x 1 = 2
2 x 2 = 4
4 x 2 = 8
8 x 3 = 24 (Krypto)

All five cards were used once and only once to equal the Objective Card.

Another Example:
Cards: 1, 3, 7, 1, 8= 1 (Objective Card)
3 - 1 = 2
7 + 2 = 9
9 / 1 = 9
9 - 8 = 1 (Krypto)

Here is a more difficult hand:
Cards: 24, 22, 23, 20, 21 = 1 (Objective Card)
24 + 22 = 46
46 / 23 = 2
2 + 20 = 22
22 - 21 = 1 (Krypto)

Score Keeping Rules:

Ten hands of Krypto equal one game. Players receive one point for
each "Krypto". Players receive double their previous hand score each
time they "Krypto" repetitively in sequence. A score returns to "1"
when sequence is broken. When players "Krypto" in error, they receive
a minus one (-1) in the score box for that hand. They are also
eliminated from play of that hand only and the hand is re-dealt for
the remaining players. All players are then eligible to score the
next hand unless another error in "Kryptoing" occurs.

Example of Score Keeping
|----------------------------------------------------------------------|
| Example: Krypto Score Pad (MPH logo) |
|----------------------------------------------------------------------|
| Players |Hand|Hand|Hand|Hand|Hand|Hand|Hand|Hand|Hand|Hand| Highest |
| | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 |Score Wins|
|----------------------------------------------------------------------|
| Debbie | 1 | | | | | | 1 | | | | 2 |
|----------------------------------------------------------------------|
| Mike | | 1 | | | | | | | | | 1 |
|----------------------------------------------------------------------|
| Shelley | | | 1 | 2 | 4 | | | | | 1 | 8 Winner |
|----------------------------------------------------------------------|
| Kim | | | | | | 1 | | | | | 1 |
|----------------------------------------------------------------------|
| Mary | | | | | | | | 1 | 2 | | 3 |
|----------------------------------------------------------------------|

* Score ties are broken by playing additional hands

Variations on the Game

Although the numerical distribution of the official Krypto deck tends to provide for more balanced games, it is possible to play Krypto with any six numbers. Many programs exist on the internet

Internet

The Internet is a global system of interconnected computer networks that use the standard Internet protocol suite to serve billions of users worldwide...

 that can generate six numbers and allow one to manipulate them with arithmetic operations. Because of the simple nature of the game, it is easy to program krypto on most scientific calculator

Scientific calculator

A scientific calculator is a type of electronic calculator, usually but not always handheld, designed to calculate problems in science, engineering, and mathematics...

s.
Versions of Krypto that only use a smaller range of numbers (such as 1-10) are better suited for beginners, while conversely, one could play a game of Krypto with a larger range of numbers that would be more difficult.