Question

if have school started at 12.15 and finished at 5.15 .the break was 30 minute. how much time did he spend in classrooms

Answer 1

4 hours and 30 minutes

Answer 2

school started at 12.15 and finished at 5.15 
total duration= 5 hours(300 minutes)
in that break was 30 minute
so time  he spend in classrooms=300-30
                                                    =270minute
                         hours=270/60
hours=4.5 ; minutes=270