## Reflection: Coherence Divisibility Rules Foldable - Section 2: Designing the Foldable

As we were reviewing all of the divisibility rules to include in the Foldable, students again questioned why we weren't including 7.  Previously, I told them that the rule for 7 is a little complicated and it may not be a shortcut.  I realized that just telling students was not enough and they still questioned the rule.

I decided to share with students one of the divisibility rules for 7 (there are a few), and let them determine if they would be using the rule in the future.

Example Divisibility Rule for 7: Take the last digit, double it, and subtract it from the rest of the number. If you get an answer divisible by 7 (including zero), then the original number is divisible by 7.  If you don't know the new number's divisibility, you can apply the rule again.

I took the students through two examples. The first number was 343, a small number, where students could fairly easily use the rule.  The second number I chose was 4,598,764.  Students quickly determined that the rule (shortcut) was too lengthy to use and that they'd rather use long division.

I think it was beneficial to expose my students to the Divisibility Rule for 7 so that they can decide for themselves if it is useful.

Why not 7?
Coherence: Why not 7?

# Divisibility Rules Foldable

Unit 3: Divisibility Rules
Lesson 4 of 5

## Big Idea: A hot dog fold serves as a divisibility rules study guide.

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40 minutes

### Ursula Lovings

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