How many rays can made from $4$ collinear points?
The answer is $6$ (as floating around the internet) but I am not sure how is it possible, as far I know geometrically a ray is a line with one end point.
We can think of a ray as being determined by two points: an endpoint and a second point that determines the direction. Let the four collinear points be $A$, $B$, $C$, and $D$, in that order.
So there are $1+2+2+1=6$ possible distinct rays that we can name using those four collinear points.
edit Let me emphasize that I've made a jump in assuming that the intended question was "How many distinct rays can be named using pairs of points from the set of 4 collinear points?"
Let the points be $A,B,C,D$, in that order on some line segment. The rays are $AB$ extended, $BC$ extended, $CD$ extended, $BA$ extended, $CB$ extended, and $DC$ extended.