1 new light fixture = 20 minutes24 new fixtures = 24 x 20 = 480 min
we know,480 min = 60min x 8 hour (a day of work )
total = 4 floors1 floor > 24 fixtures = 1 day2 floor > 24 fixtures = 1 day3 floor > 24 fixtures = 1 day4 floor > 24 fixtures = 1 day >> total 4 days ( 8hrs each day)
from question, we found that: For 24 fixture - he needs 480 min(or 8hr) which is nothing but 1 work day. now,1 floor > 24 fixtures = 1 day 2nd floor > 24 fixtures = 2nd day
..... And on 4th Day he finishes,a) Floor >1 floor + 2 floor + 3 floor + 4 floor b) Fixture> 24+24+24+24 = 96 fixturesc) Days> 4 days.
