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MathBait™ Multiplication

Guess Who

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Amp up multiple fluency as well as build a strong foundation for common factors with this Napier's Bones activity. Students must consider questions that will have the most impact while building familiarity with their own rod as they try to be the first to identify their partner's bone.


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Playing with Napier's Bones







This game is ideal for students working on building fluency with multiplication.

Arrange students in groups of two and provide them with a half-set of bones (one bone for each digit) placed face down between them.

Each player selects a rod in secret, not showing it to their teammate.

Players take turns asking their partner questions. For instance, "Is 36 a multiple of your number?". For an added challenge, only allow students to ask questions about one digit at a time. Questions can be, "how many zeros are on your rod?", or "do you have any 5's in the ones place?"

Students playing one has a 3-rod, the other asks if 36 is a multiple of her number

The first student to guess the other player's rod wins.

Note: Be careful with terminology and setting the rules. For instance, in the image above 36 is a multiple of 3 although it is not shown on a standard bone. Students may ask "Is 36 a multiple on your bone?" or, for added challenge, allow students to guess questions that may not appear on the bone itself.

This game elicits thinking about common multiples as students consider what questions will have the most impact. Students are building familiarity with their "cards" as they must examine its values. Guess Who can also encourage vocabulary as teachers may require students to use words like "multiple", "factor", or even "divisible by" depending on student level.

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