2000004503

SubArea: 
Combinatorics
Level: 
A
Project ID: 
2000004503
Accepted: 
0
Clonable: 
0
Easy: 
1
How many lines are determined by 6 different points in the plane, if any three of the points do not lie in one straight line?
(62)=15
6!2!=360
(63)=20
6