There are 5 points on the plane, no three points are collinear, and any three points form a triangle, what is the number of triangles?
平面上有5个点，无三点共线，以任意三点组成一个三角形，则三角形的个数应为多少．
<gadget id="calculator">5 * 4</gadget>
<output>20</output>

<gadget id="calculator">20 / 2</gadget>
<output>10</output>

<result>10</result>