Thank you for your interest in NCTM’s Illuminations. Beginning in mid-April, all Illuminations content will be moving to nctm.org/illuminations. Interactives will remain openly available and NCTM members will have access to all Illuminations lessons with new filtering and search options. We hope you will continue to utilize and enjoy these resources on nctm.org.

## Primary Krypto

Pre-K-2, 3-5, 6-8
Standards:
Math Content:
Number and Operations

The rules of Krypto are simple: Combine five number cards using the four arithmetic operations (+, –, ×, ÷) to arrive at a "target" number. This online version of Primary Krypto uses the numbers 1–10 only.

• Drag-and-drop the number cards onto the game board. They will snap into place on the outlined squares. From the small squares, choose which operation is to be performed.
• The three buttons are used to control the game:
• deal - get a new set of number cards and a new target number
• hint - for the current hand, reveal one possible set of operations that yield a solution
• solve - see our solution (though not necessarily the only solution)

• Click deal to generate a set of number cards and a target number. Find a solution for the puzzle. Then, click the hint button if you did not find our solution. Can you find a solution that uses the operations in the order supplied by the hint?
• What problem-solving strategies can be used while playing Primary Krypto?