Question 10

Let positions 1 to 6 represent heights from tallest (1) to shortest (6).

• Observation II: $Q$ is the shortest of all, so position 6 is $Q$.
• Observation III: $U$ is taller than only one student ($Q$), so position 5 is $U$.

The remaining students $P, R, S, T$ occupy positions 1, 2, 3, 4.

• Observation I: $S > R$.
• Observation IV: $T > S$ but $T$ is not the tallest. Thus $T$ cannot be at position 1. Since $T > S > R$, the three students $T, S, R$ must take positions 2, 3, 4 respectively.
• Consequently, position 1 must be $P$.

The complete descending height order is:

Students taller than $R$ are $P, T, S$ (3 students). We look for a student who has exactly 3 students shorter than them:

• Students shorter than $S$ are $R, U, Q$ (3 students).

Hence, the number of students taller than $R$ is equal to the number of students shorter than $S$.