(Q1)Some points are plotted on a plane. Each point is joined with all remaining points by line segments. Find the number of points if the number of line segments are 10.

Answer

Number of distinct line segments that can be formed out of n-points =
n(n-1)
2
Given:Number of line segments
n(n-1)
2
 = 10

n2 - n = 20

n2 - n - 20 = 0

n2 - n + 4n - 20 = 0

n(n-) +4(n-) = 0

(n-)(n + 4) = 0

n- = 0 (or) n + 4 = 0

n = (o)r -4

∴n = [n - can't be negative]