We are asked to determine the total number of students in a school. To do that we need to add the number of students in each of the year classes. Beginning with the 9th class we have:
![N_9=300](https://img.qammunity.org/2023/formulas/mathematics/high-school/a5ae2lrrcqllywhdemtfeuupx9x8m27anm.png)
Now, the number of students in the 10th year class is 20% more, this means:
![N_(10)=300+300*(20)/(100)=360](https://img.qammunity.org/2023/formulas/mathematics/high-school/4yiui77cmjlk7tos3cx9camsdw3jvvgfb9.png)
Now, the number of students in the 11th year class is:
![N_(11)=360+360*(20)/(100)=432](https://img.qammunity.org/2023/formulas/mathematics/high-school/57ymkag82gzt61vii7g7437hfyyp7zer7p.png)
The 12th year class is:
![N_(12)=432+432*(20)/(100)=518.4](https://img.qammunity.org/2023/formulas/mathematics/high-school/zqyp7uwidc3gq92w11eq4ps7fndsa5mcrt.png)
Now we add all the students in each class:
![\begin{gathered} N=N_9+N_(10)+N_(11)+N_(12) \\ N=300+360+432+518.4 \\ N=1610.4 \end{gathered}](https://img.qammunity.org/2023/formulas/mathematics/high-school/abr535dlpfjr6ju0y2trchwplgcravhw4f.png)
Therefore, there are about 1610 students in Townsend High School.