CAPF AC 2021 Q55: General Mental Ability – Logical Reasoning & Puzzles
- (a) Friday
- (b) Tuesday
- (c) Saturday
- (d) Monday
Answer: (d) Monday
Explanation
Day of the week one year on
Given: the first March of a year is a Sunday; find the day on the first February of the next year.
How to think: count the days between the two dates and take the remainder on dividing by 7.
Both dates lie after one February and before the next 29 February, so a leap year makes no difference.
| Month | Days counted |
|---|---|
| March | 31 |
| April | 30 |
| May | 31 |
| June | 30 |
| July | 31 |
| August | 31 |
| September | 30 |
| October | 31 |
| November | 30 |
| December | 31 |
| January | 31 |
| Total | 337 |
Odd days: 337 = 48 × 7 + 1.
So the day moves forward by one.
Sunday + 1 = Monday.
Answer: (d) Monday.
Why each option is right or wrong
- (a) Incorrect. Friday would need 5 odd days; there is only 1.
- (b) Incorrect. Tuesday would need 2 odd days, for example by wrongly adding a leap day.
- (c) Incorrect. Saturday would mean going back a day, but the date moves forward.
- (d) CORRECT. 337 days leave 1 odd day, so Sunday becomes Monday.
Key point
Odd days = total days mod 7. From 1 March to 1 February next year is always 337 days (1 odd day), whether or not either year is a leap year.
Remember
337 days = 48 weeks + 1 day.
Common mistakes
- Adding an extra day for a leap year, though 29 February never falls in this gap.
- Counting February's 28 days as well, which overshoots to 1 March.
- Dividing by 7 wrongly: 337 leaves a remainder of 1, not 2.
Exam tip
Educated guess: 1 March to 1 March next year is 365 days, which is 1 odd day (Monday) in a normal year. Going back 28 days to 1 February is exactly 4 weeks, so the day stays Monday.
Sources
- NCERT Class VI Mathematics — Knowing Our Numbers and Playing with Numbers (divisibility and remainders)
- R. S. Aggarwal, A Modern Approach to Verbal and Non-Verbal Reasoning — Calendar