91Ó°ÊÓ

The total number of students is $50$, the number of students in one course is $30$and the number of students in $2$courses is $15$.

Number of students in three courses $$\begin{gathered} =50-30-15 \\ =5 \end{gathered}$$

Relative frequency for 2 courses localid="1647583818357" $=\frac{numberofstudentsin2courses}{Totalstudents}$

$$\begin{gathered} =\frac{15}{30} \\ =0.3 \end{gathered}$$

localid="1647583898921" $$\begin{gathered} \text{Relativefrequencyfor3courses}=\frac{numberofstudentsin2courses}{Totalstudents} \\ =\frac{5}{50} \\ =0.10 \end{gathered}$$

Cumulative relative frequency of $1$courselocalid="1647609706501" $=0.6$

Cumulative relative frequency of $2$course$=0.6+0.3=0.9$

Cumulative frequency of $2$course$=0.6+0.3+0.1=1$

Total number of students is $50$, number of students in one course is $30$and number of students in $2$courses is $15$

$$\begin{gathered} Percent=\frac{numberofstudentsin2courses}{totalumberofstudents}×100 \\ =\frac{15}{50}×100 \\ =30\% \end{gathered}$$

Total number of students is $50$, number of students in one course is $30$and number of students in $2$courses is $15$

$$\begin{gathered} Percent=\frac{numberofstudentsin1or2courses}{totalumberofstudents}×100 \\ =\frac{30+15}{50}×100 \\ =90\% \end{gathered}$$