6:30-11:15=18.50-11.25=7.25 hours or 29/4hr.
25 mins=25/60=5/12hr; 1:30=1.5=3/2hr. Length of work time plus break time=3/2+5/12=18/12+5/12=23/12.
(29/4)/(23/12)=(29/4)(12/23)=87/23=3.8 approx. So there can be no more than 3 breaks.
SCHEDULE
11:15+1:30=12:45 (1st break start)
12:45+0:25=13:10 (1st break end)
13:10+1:30=14:40 (2nd break start)
14:40+0:25=15:05 (end of 2nd break)
15:05+1:30=16:35 (3rd break start)
16:35+0:25=17:00 (end of 3rd break)
17:00-18:30 (last work session)
The schedule confirms that staff have three breaks each day.