5 points are marked on a straight line and another 6 points are marked on a second straight line ...
5 points are marked on a straight line and another 6 points are marked on a second straight line with no points in common. How many triangles can be constructed with vertices from among the above points?
Answer/Solution
5
Steps/Work
assuming that the top line can have either 2 points or 1 point...
5! / 1!4! - 5! / 2! 3! yields 5.
B
5! / 1!4! - 5! / 2! 3! yields 5.
B