The number of rotation done by hour hand in 12 hr is 360 degree. So hour hand rotates in one hour is,
[tex]\frac{360}{12}=30[/tex]The number of hours covered by hour hand from 3 to 9 is 6 hours.
Determine the angle in degree for 6 hours rotation by hour hand.
[tex]6\cdot30=180[/tex]So hour hand moves by 180 degrees.
