Find the value of the combination.

how many straight lines can be drawn through 20 points, of which no three lie on any one straight line?

a. 190
b. 380
c. 1,140

Combination formula:

n C r = (n!)/(r!(n-r)!)

20 C 2 = (20!)/(2!*(20-2)!)

20 C 2 = (20!)/(2!*18!)

20 C 2 = (20*19*18!)/(2!*18!)

20 C 2 = (20*19)/(2!)

20 C 2 = (20*19)/(2*1)

20 C 2 = (380)/(2)

20 C 2 = 190



Or as a simpler alternative

20*19/2 = 380/2 = 190



Either way, the final answer is choice A) 190