1. **State the problem:** A school has admitted 480 senior one students divided into four classes A, B, C, and D. Class A has 80 students. The ratio of students in class B to class C is 2:3. The number of students in class A is twice the number in class D. We need to find the number of students in class C to determine how many single seater chairs are needed. 2. **Define variables:** Let the number of students in class D be $d$. Then, the number of students in class A is $80$ (given), and $80 = 2d$. 3. **Find $d$:** $$80 = 2d \implies d = \frac{80}{2} = 40$$ 4. **Express students in classes B and C:** Let the number of students in class B be $b$ and in class C be $c$. Given the ratio $b:c = 2:3$, so $b = 2k$ and $c = 3k$ for some $k$. 5. **Use total students to find $k$:** Total students = $480$. Sum of students in all classes: $$80 + b + c + d = 480$$ Substitute $b = 2k$, $c = 3k$, and $d = 40$: $$80 + 2k + 3k + 40 = 480$$ $$120 + 5k = 480$$ $$5k = 480 - 120 = 360$$ $$k = \frac{360}{5} = 72$$ 6. **Find number of students in class C:** $$c = 3k = 3 \times 72 = 216$$ **Final answer:** The number of students in class C is $216$, so the academic officer needs to get 216 single seater chairs for class C.