A class starts at 11:00 am and lasts till 2:27 pm. Four periods of equal duration are held during this interval. After every period, a rest of 5 minutes is given to the students. The exact duration of each period is :
- (a) 48 minutes ✓ UPSC's answer
- (b) 50 minutes
- (c) 51 minutes
- (d) 53 minutes
Why the answer is (a)
• 11:00 am to 2:27 pm is 3 hours 27 minutes = 207 minutes.
• Four equal periods have three 5-minute rests between them (the rest after the last period falls outside the class), i.e. 15 minutes of rest.
• So 4 × (period) = 207 – 15 = 192 minutes, and each period is 192 ÷ 4 = 48 minutes.
• Check: 48 + 5 + 48 + 5 + 48 + 5 + 48 = 207 minutes.
• Hence 48 minutes, option (a).
Why the other options are wrong
- (b) 50 minutes
- 50 minutes would require a total class time of 215 minutes (3 hours 35 minutes), which exceeds the given 207 minutes.
- (c) 51 minutes
- 51 minutes would require a total class time of 219 minutes (3 hours 39 minutes), which is inconsistent with the 207-minute duration.
- (d) 53 minutes
- 53 minutes would require a total class time of 227 minutes (3 hours 47 minutes), which is significantly longer than the actual class duration.
Asked in the CSAT Paper II of the UPSC Civil Services Preliminary Examination 2016, held on 7 August 2016. Question and answer key: Union Public Service Commission. Explanation: UPSC Answer Check.