COMBINATIon question (1 Viewer)

[gamecw]

i dont get what this question is saying!

find the number of ways in which a pair of triangles can be drawn with 6 given points as vertices, no three of the points being collinear.

a pair of triangles? what?

solution is 10

sumone help

 

[webby234]

You have six points, of which you are choosing three to form triangles. So the number of possible different triangles is 20 (6C3). But as you are forming a pair of triangles, choosing three points is equivalent to choosing the remaining three points so you must divide by 2, getting 10.

 

[gamecw]

tx

 

[followme]

what difference would it make if 3 pts were collinear?

 

[BIRUNI]

If 3 points are collinear, then you will not be able to make a triangle; you can make a straight line.

 

[followme]

How about
. . . and
. . .

. . .
. ...
. .

i suppose they can still form triangles..

 

[pLuvia]

How about
. . . and
. . .

. . .
. ...
. .

i suppose they can still form triangles..

Of course, but then they'll just be a restriction on the combination wouldn't there