A science class has 3 girls and 3 boys in the seventh grade and 7 girls and 1 boy in the eighth grade. The teacher randomly selects a seventh grader and an eighth grader from the class for a competition. What is the probability that the students she selects are both girls?

Answer 1

independent events
... multiply the individual probabilities to find the probability of both

probability of 7th grade girl is ... 3 / (3 + 3)

probability of 8th grade girl is ... 7 / (7 + 1)

Answer 2

Prob(girl from 7th grade) = 3/6 = 1/2
prob(girl from 8th grade) = 7/8
prob(both girls) = (1/2)(7/8) = 7/16