A Problem For you all:
Number of quadrilaterals which can be formed by joining the vertices of a decagon so that none of the sides of the quadrilateral is also a side of the decagon is _______?

Question

A Problem For you all:
Number of quadrilaterals which can be formed by joining the vertices of a decagon so that none of the sides of the quadrilateral is also a side of the decagon is _______?

experimentx · Answer

12x11x8x7??

anonymous · Answer

its less than 210 i think

anonymous · Answer

@eigenschmeigen  - Agreed.
@experimentX  - Whats the logic?

experimentx · Answer

Oh ... i thought i was dodecagon ... 
10*9*6*5 <----i was thinking ... but seems wrong

anonymous · Answer

it has to be less than 10C4 as that would be the total number of quadrilaterals. i think it's less than 200, and i'm narrowing it down

anonymous · Answer

@eigenschmeigen  -- Absolutely. 
@experimentX  -- Yeah. That is wrong. Definately,

experimentx · Answer

112?

anonymous · Answer

ok, i'm less sure, but i think it's less than 50

anonymous · Answer

^^ Youre right so far.
How?

anonymous · Answer

i'll say in just a sec, i'm on the last bit

asnaseer · Answer

|dw:1337452847748:dw|
I get 40