out of 18 points in plane, no three are in the same straight line except 5 points which are collinear.
then the number of straight lines obtained by joining them is ??
Answers
Answered by
5
Step-by-step explanation:
Given :
Total points =18
Collinear points =5
No of lines formed from 18 points =18C2
(Since we require two points to form one line.)
Five points are collinear =5C2
⇒Required no of straight line =18C2−5C2+1
18C2=18!2!16!
⇒18×17×16!2×1×16!
⇒162
5C2=5!2!13!
⇒5×4×3!2×3!
⇒10
18C2−5C2+1=153−10+1
⇒143+1
⇒144
Similar questions