Question

To pick a lab partner, each student must write his/her name down on a piece of paper and drop it into a bowl. Students would then pick the pieces of paper from that bowl to get their lab partners. Given that Kevin was the first one to pick a chit and he has 5 friends in his class and there are 20 students in the class, what is the probability that Kevin's partner will be one of his friends?

• A. $P\left(\text{lab partner is Kevin's friend}\right)=0\%$
• B. $P\left(\text{lab partner is Kevin's friend}\right)=25\%$
• C. $P\left(\text{lab partner is Kevin's friend}\right)=50\%$
• D. $P\left(\text{lab partner is Kevin's friend}\right)=75\%$

Answer 1

The correct option is B $P\left(\text{lab partner is Kevin's friend}\right)=25\%$

Number of pieces of paper $=20$
Number of pieces of paper with Kevin's friend's name on it $=5$
Therefore,
$P\left(\text{lab partner is Kevin's friend}\right)=\frac{5}{20}=\frac{1}{4}$
$P\left(\text{lab partner is Kevin's friend}\right)=25\%$