A classroom clock shows 9:15. What is the smaller angle between its two hands?

Explanation

1. 01

   $|30 \times 9 - 5.5 \times 15| = |270 - 82.5| = 187.5^\circ$.

2. 02

   That is more than $180^\circ$, so the smaller angle is $360 - 187.5 = 172.5^\circ$.