Brittany has ten friends helping with a school fundraiser.

Question

Brittany has ten friends helping with a school fundraiser. There are 3 girls and 7 boys. She needs two people to be in charge of the cash register. What is the probability that both of them are boys or both of them are girls?

A. 100%
B. 53%
C. 58%
D. 5%

Answer 1

Brittany,

 

A probability requires dividing by a total number of possibilities so we're looking at how many groups of 2 can be chosen from 10. Order does not matter so use a combination (10 choose 2)=45 total possibilities.

 

We want to look at possibilities that they are both boys or girls, so add combination 3 choose 2 and combination 7 choose 2:

(3+21)/45=.533 or 53%

 

Hope that helps!