Answer:
[tex]\frac{7}{44}[/tex]
Explanation:
Probability refers to the chance of occurrence of some event.
Number of building sites for factories = 12
Number of toxic waste sites = 5
So, number of non-toxic waste sites = 12 - 5 = 7
We need to find the probability that the 3 sites chosen for initial building locations are non-toxic.
Solution:
Probability = number of non-toxic waste sites / Number of building sites for factories = [tex]\frac{7_{C_{3}}}{12_C_{3}}=\frac{\frac{7!}{3!4!}}{\frac{12!}{3!9!}}=\frac{7\times 6\times 5}{3\times2}\times\frac{3\times2}{12\times11\times10}=\frac{7}{44}[/tex]