Thursday

November 20, 2014

November 20, 2014

Posted by **Nichole** on Wednesday, December 14, 2011 at 11:56pm.

- math -
**MathMate**, Thursday, December 15, 2011 at 3:25amNumber of possible choices for the first point = 9.

Number of possible choices for the second point = 8.

Number of possible choices for the third point = 7.

Possible triangles with specific order of points = 9*8*7 = 504.

However, when we say triangle, we are not really concerned in which order the points are selected. So we have*over-counted*the number of triangles by 6, which is the number of ways to order three points.

The number of*distinct*triangles is therefore 504/6=84.

This number is mathematically called

9 choose 3, calculated by

9!/(3!(9-3)!) = 84

where 9! is factorial 9, = 9*8*7*...*2*1

**Answer this Question**

**Related Questions**

geometry - Please help me to draw this figure four points that are not collinear...

math - My son has been given the collinear problem below that has be stumped two...

Math - explanation - This is an example in the text book. Using vectors, ...

math - suppose n points are in space, no three are collinear and no four or are ...

math - a triangle is a figure formed by three segments connecting three ...

Math - Three points D, E, and F are collinear. Is there only one plane that ...

Calculus II - show that; given any three non-collinear points (x1,y1), (x2,y2...

Geometry - Plese show how it is possible for two triangles to intersect in one ...

math - Two different relationships are shown below. Relationship 1: xy = 3 ...

math - Are three collinear points are always also coplanar points.