There are m boys and 12 girls in a class. What is the probability of selecting at random a girl from the class?

A.
(frac{m}{12}) 
B.
(frac{12}{m}) 
C.
(frac{12}{m+12}) 
D.
(frac{12}{m12})
Correct Answer: Option C
Explanation
Prob. (a girl) (=frac{Numberhspace{1mm} ofhspace{1mm} girls}{Number hspace{1mm} of hspace{1mm} boys hspace{1mm} and hspace{1mm} girlshspace{1mm} in hspace{1mm} class}\
= frac{12}{m+12})