Sushma Saroj
Sushma Saroj
2 years ago

Here is 15 dots. If you select 3 dots randomly, what is the probability that 3 dots make a triangle?

A. 412/455

B. 440/455

C. 449/455

D. 438/455

Solution(By Examveda Team)


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 = 43.
So we can form a triangle in 455 - 43 = 412.
So probability could be 412/455.

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Comments ( 3 )

  1. Sushma Saroj
    Sushma Saroj :
    2 years ago

    Excellent explanation.It is really very good site.God bless u examveda.My all problems solve there.Thank u soooooo much

  2. Sushma Saroj
    Sushma Saroj :
    2 years ago

    plz explain sudhakar.I need complete explanation

  3. Sudhakar Prajapati
    Sudhakar Prajapati :
    2 years ago

    412/455

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