Posted by **please help** on Monday, January 14, 2013 at 8:18pm.

distint points a, b, c, d, e, and f are marked on a circle. How many triangles can be formed using these points as vertices?

- geometry -
**Allyson**, Monday, January 14, 2013 at 8:20pm
Draw a circle, form as many triangles as you can, and count.

- geometry -
**please help**, Monday, January 14, 2013 at 8:23pm
ok i tried that that its hard why don't u try and tellme the answer ?

- geometry -
**Reiny**, Monday, January 14, 2013 at 8:35pm
You have 6 points on a circle.

It is not possible to have 3 of them forming a straight line (not a triangle) so the question becomes how many choices are there of 3 elements form 6

or C(6,3) = 6!/(3!3!) = 20

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