Imagine that you have five points in the plane, no three of them in a straight line.
a. Imagine drawing a straight line segment between each pair of points. How many lines would you get?
(Hint: each line segment will be drawn between a pair of points. How many pairs of points can you make from a set of five points?)
Answer: 20
b. Now suppose there are not five but twelve points in the plane, no three of them in a straight line. How many lines would you get?
Answer: 132
I'm confused if I should use Permutation or Combination. Please help. Thanks.
Permutation
a: 20
b: 132
Combination.
a: 10
b: 66
a. Imagine drawing a straight line segment between each pair of points. How many lines would you get?
(Hint: each line segment will be drawn between a pair of points. How many pairs of points can you make from a set of five points?)
Answer: 20
b. Now suppose there are not five but twelve points in the plane, no three of them in a straight line. How many lines would you get?
Answer: 132
I'm confused if I should use Permutation or Combination. Please help. Thanks.
Permutation
a: 20
b: 132
Combination.
a: 10
b: 66