Constant Rule? Why do we have to divide by 6?

  • ADMIN M0★ M1 M5

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  • ADMIN M0★ M1 M5

    [Originally posted in Discussions]

    Module 0 Week 2 Day 8 Challenge Explanation

    So when Professor Loh said that you have to divide by half because you would've counted every intersection twice with 6 times 5 using the rule 6 choose 2, does that mean you have to divide by 2 after multiplying for every single question of this type?

  • ADMIN M0★ M1 M5

    Thanks for asking! It's not always true that you must divide by 2 to eliminate the copies, because sometimes you divide by other numbers. You can look at the long response to your earlier question. The number of triangles was

    97c7839b-c531-4573-9e13-0c4872c7c96f-image.png
    and we divided by 3!, which equals 6, because there are 6 copies of each way to make a triangle. These are the six ways to make a triangle with the red line, dark green line, and yellow line:

    M0W2D8-ch-lines-red-green-yellow-triangle-group-smaller.png
    The number of copies per way depends on the question.

    I hope this helps! Good luck on the rest of the course, and please ask if you have any more questions!

    Happy Learning,

    The Daily Challenge Team