A math class has 7 girls and 5 boys in the seventh grade and 4 girls and 4 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 she selects two boys?

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Answer 1 · 2017-01-23T09:56:55

#20/96=5/24~=21%#

To find the probability of picking two boys, we need to first know how many different ways she can pick the 7th and 8th grader.

There are 12 7th-graders and 8 8th-graders. So the total number of ways she can pick is:

#12xx8=96#

To get two boys picked, there are 5 boys in the 7th-grade class and 4 in the 8th-grade class, so there are:

#5xx4=20# ways

Which gives us the probability of:

#20/96=5/24~=21%#