pnc doubt

A regular polygon of 10 sides is constructed. No. of ways 3 vertices be selected so that no two vertices are consecutive is..... i understand this and but i tried using a diff method and it didnt come right...if i arrange the 7 gaps between 3 vertices ensuring theres always one in between 2 vertices i'll get x + y + z =4 and so i'll get 6c2 = 15...why isnt this approach correct?
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16 Replies
iTeachChem Helper
@Apu
iTeachChem Helper
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iTeachChem Helper
@Apu
iTeachChem Helper
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Ace007
Ace007OP2mo ago
sorry for the double ping 🙏
Gamertug
Gamertug2mo ago
i dont think that will be possible what abotu when 2 sides are consecutive it doesnt count that i mean 2 points are consecutive and there are also those triangles for which all 3 points are consecutive at corners
Ace007
Ace007OP2mo ago
no 2 vertices should be consecutive right so i just arranged the 7 vertices between any 3 oh wait 😭 i forgot to choose those 3 first
Gamertug
Gamertug2mo ago
they can
Ace007
Ace007OP2mo ago
its in the question
Gamertug
Gamertug2mo ago
nvm am dumb
Ace007
Ace007OP2mo ago
no worries 😭 im dumb too
Gamertug
Gamertug2mo ago
hmmm
Ace007
Ace007OP2mo ago
accha i think i got it 10 ways to select a starting point...then 15 ways for division of gaps...divided by 3 since vertices arent distict
itsav23
itsav232mo ago
okie so from what i could get, you're trying to place 3 vertices with at least one gap between them but that doesn't account for all positions correctly. Instead think of it like thi....place the 7 empty spots first and then pick 3 out of the remaining 7 positions for the vertices.
Ace007
Ace007OP2mo ago
hm?
iTeachChem
iTeachChem2w ago
all g?

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