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virtus

  • 3 years ago

9 dots are drawn as below. How many triangles can be formed by joining three dots?

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  1. virtus
    • 3 years ago
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    |dw:1342275033333:dw|

  2. virtus
    • 3 years ago
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    @UnkleRhaukus hope your not here to troll me again

  3. UnkleRhaukus
    • 3 years ago
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    thats not my style @virtus

  4. UnkleRhaukus
    • 3 years ago
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    i can see four 2x2 triangles

  5. UnkleRhaukus
    • 3 years ago
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    16, 1x1 triangles

  6. UnkleRhaukus
    • 3 years ago
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    i suppose the dont have to be right angles

  7. ash2326
    • 3 years ago
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    @virtus do you have options?

  8. virtus
    • 3 years ago
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    not sure what you mean by options @ash2326 but incase you were wondering, my solution book says 9C3 -8

  9. virtus
    • 3 years ago
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    @UnkleRhaukus you have PARTIALLY redeemed yourself

  10. UnkleRhaukus
    • 3 years ago
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    i feel better already,

  11. virtus
    • 3 years ago
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    good to know, why don't you change feeling "good" to "euphoric" by suggesting why the answer is 9C3 -8

  12. UnkleRhaukus
    • 3 years ago
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    say you want to find all the triangle that have the top left as a vertex, how many can you make

  13. mukushla
    • 3 years ago
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    9C3 -triples which are in the same line=9C3-8 |dw:1342275604359:dw|

  14. UnkleRhaukus
    • 3 years ago
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    i count eighteen |dw:1342275638118:dw|

  15. UnkleRhaukus
    • 3 years ago
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    19,20|dw:1342275746454:dw|

  16. UnkleRhaukus
    • 3 years ago
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    there are so many

  17. virtus
    • 3 years ago
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    but hows that joining three dots?

  18. UnkleRhaukus
    • 3 years ago
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    mukushla is right , we are misusing the straight lines because they are not triangles

  19. mukushla
    • 3 years ago
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    different triangles can be formed by joining 3 of the dotes unless 3 dots are in the same line, so C(3,9)-8

  20. virtus
    • 3 years ago
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    but why is do we minus 8

  21. virtus
    • 3 years ago
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    *why do we

  22. mukushla
    • 3 years ago
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    u can count triples of dots that are in the same line just like what i did up there

  23. UnkleRhaukus
    • 3 years ago
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    this is not a triangle |dw:1342276198984:dw|

  24. virtus
    • 3 years ago
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    oh ok

  25. sarthak810
    • 3 years ago
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    6

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