Question

It was 9/20 ..

A math class has 9 girls and 1 boy in the seventh grade and 2 girls and 2 boys 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?

Write your fraction in simplest form.

Answer 1

`(9)/(20)`

Explanation:

We want probability that 1st is girl AND 2nd is girl as well.

In probability "AND" means multiplication and "OR" means "addition".

We find the probabilities separately and multiply them together, since "AND".

• P(girl from 7th grader) = number of girl 7th grader/total number of 7th grader

=9/10

• P(girl from 8th grade) = number of girl in 8th grade/total number of 8th grader

=2/4

P(both girls) = 9/10 * 2/4 =9/20