UPSC Prelims 2016 · CSAT
Question 26: Basic Numeracy
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 :
AnswerUPSC’s answer is (a).
Total time from 11:00 am to 2:27 pm is 3 h 27 min = 207 min. Four periods have three rests between them (none is needed after the last period, as the class ends): 3 x 5 = 15 min. Teaching time = 207 - 15 = 192 min, so each period = 192 / 4 = 48 min. Check: 4 x 48 + 15 = 207. Remember: n periods have n - 1 breaks between them.
Why each option is right or wrong
- (a) Right: 192 minutes of teaching over 4 periods gives 48.
- (b) 50 minutes: 4 x 50 + 15 = 215, too long.
- (c) 51 minutes: 4 x 51 + 15 = 219, too long.
- (d) 53 minutes: 4 x 53 + 15 = 227, too long.
Answer: UPSC’s key. Explanation: written by UPSC Grade, not by UPSC.
Source: UPSC, Civil Services (Preliminary) Examination 2016, General Studies Paper II (CSAT), Series A. The paper on upsc.gov.in.