Step-by-step explanation:
what should be the question ?
how many different pairs of 2 girls can you pick out of 8 ?
what is the probability that a specific girl is in the picked pair ?
or is it : if you pick randomly 2 students from the class, what is the probability to have picked 2 girls ?
and there are more options.
but I assume the problem is the picking randomly 2 students.
so, it is 20 students (12 + 8). if we pick 1 student, we have a chance of 12/20 = 3/5 to pick a boy, and a chance of 8/20 = 2/5 to pick a girl.
in our experiment we pick 2 students in a row without returning the first pick into the main pool.
the probabilty for the first pick to be a girl is, as mentioned, 2/5 or 0.4.
for the second pick we have only 7 out of 19 choices to pick a girl. so, the probability to pick a girl now is 7/19.
the combination of both (non-overlapping) probabilities is done via multiplication, and the probabilty to pick 2 girls is :
2/5 × 7/19 = 2×7 / 5×19 = 14/95 = 0.147368421...
