Lunch break is 1 1/4 hours long

Lunch break ends at 1:30pm

At what time does it start?

Lunch starts at 1:30. So 1/4 of 1 hour is 15 minutes. Subtract 1 hour or 60 minutes from 1:30, which equals 12:30. So you have 1/4 remaining, so subtract 15 minutes from 12:30, giving you a final answer of 12:15.