An office opens at 9 a.m. and closes at 5.30 p.m. with a lunch break of 30 minutes. What is the ratio of lunch break to the total period in the office?

Lunch break period = 30 minutes

9 a.m. to 5.30 p.m. is 7 hours and 30 minutes

1 hour is 60 minutes

⇒ 7 hours = 7 × 60 = 540 minutes

Total period in office = 540 + 30 = 570 minutes

Therefore, ratio of lunch break to the total period in the office =

⇒ ratio = =

Dividing numerator and denominator by 3 we get

⇒ ratio =

Therefore, ratio of lunch break to the total period in the office is 1:18