Here is 15 dots. If you select 3 dots randomly, what is the probability that 3 dots make a triangle?	Choices.
A) 440/455
B) 412/455
C) 434/455
D) 449/455
E) 438/455
Total ways of selecting 3 dots out of 15 is 15C3 = 455 If 3 dots are collinear then triangle may not be formed. Now look at the above diagram. If we select any 3 dots from the red lines they may not form a triangle. They are 3 x 5C3 = 30. If we select the three letters from blue lines, they may not form a triangle. They are in total 5 ways. Also there are 6 others lines which don't form a triangle. Also another two orange lines. Total = 30 + 5 + 6 + 2= 
<gadget id="calculator">30 + 5 + 6 + 2</gadget>
<output>43</output>
43. So we can form a triangle in 455 - 43= 
<gadget id="calculator">455 - 43</gadget>
<output>412</output>
412. So answer could be 412/455.   ANSWER:412/455
<result>B</result>
Here is 15 dots. If you select 3 dots randomly, what is the probability that 3 dots make a triangle?