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Sides of a Triangle

Directions: The perimeter of a triangle is 20 units. Using whole numbers, how many sets of side lengths can you find for this triangle?



Can one of the side lengths be 10? Why or why not?
Can one of the side lengths be 20? or more than 20? Why or why not?
What is true about the sum of any two sides of a triangle compared to the third side?
Is a triangle with the sides 3, 4, 5 different than a triangle with the sides 4, 5, 3? Does the order matter?



2, 9, 9
3, 8, 9
4, 7, 9
5, 6, 9
6, 6, 8
7, 7, 6
8, 8, 4

These are the whole number sets of side lengths my students found. There may be more.

Source: Christina Ploeckelman

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  1. 5, 7, 8

  2. I think I know how you came up with the answers.

  3. I think I know too!

  4. Fradrick Deanjerson

    I guess I could figure it out too. Howard, do you know if that is Jacob who made his name Something?

  5. How did you know?

  6. Fradrick Deanjerson

    I saw you during math class typing that. I am so sneaky!

  7. We probably shouldn’t be talking about this on the computer where anyone can see it. 😉

  8. Fradrick Deanjerson

    K. See ya at skyzone on Thursday?

  9. You guys shouldn’t talk t each other and share your plans. Don’t do it again. I am sure your teacher is very angry.

  10. feisty!

  11. I am mad that you boys were commenting and sharing plans on a public website. And it was rude to type ‘feisty’. See me after class for that boys. I will be calling your parents too.

  12. I apologies for Jacobs behavior, Dansheil. it was very mean of them. I am so so so so so so so sorry.

  13. It is fine. Boys will be boys.

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