Source: Previous Question Papers

How many more segments are formed by joining six collinear points to each other than by joining five non-collinear points to each other?

Options

Option A

9

Option B

7

Option C

8

Option D is correct

5

Explanation

The number of segments formed by joining nn distinct points is given by the combination formula (n2)=n(n1)2\binom{n}{2} = \frac{n(n-1)}{2}.

Part 1: Segments formed by joining six collinear points. For n=6n=6 collinear points, the number of segments is (62)=6×(61)2=6×52=302=15\binom{6}{2} = \frac{6 \times (6-1)}{2} = \frac{6 \times 5}{2} = \frac{30}{2} = 15.

Part 2: Segments formed by joining five non-collinear points. For n=5n=5 non-collinear points, the number of segments is (52)=5×(51)2=5×42=202=10\binom{5}{2} = \frac{5 \times (5-1)}{2} = \frac{5 \times 4}{2} = \frac{20}{2} = 10.

To find how many more segments are formed, we subtract the second number from the first: Difference =1510=5= 15 - 10 = 5. Therefore, 55 more segments are formed.