Question: 2014 Fall Final - 12
A bowl contains 5 blue balls, 4 red balls, and 6 green balls. We choose 2 balls uniformly at random.
What is the probability that these 2 balls have the same color?
(a)
$\frac{{15 \choose 2}}{{5 \choose 2} + {4 \choose 2} + {6 \choose 2}}$
(b)
$\frac{{5 \choose 2}{4 \choose 2}{6 \choose 2}}{{15 \choose 2}}$
(c)
$\frac{{15 \choose 2}}{{5 \choose 2}{4 \choose 2}{6 \choose 2}}$
(d)
$\frac{{5 \choose 2} + {4 \choose 2} + {6 \choose 2}}{{15 \choose 2}}$