Mr ‘X’ has three children. The birthday of the first child falls on the 5th Monday of April, that of the second one falls on the 5th Thursday of November. On which day is the birthday of his third child, which falls on 20th December?
Answer & explanation
Answer: (b) Thursday
Only one start works for both clues: 1 April a Sunday, which makes 1 November a Thursday. Counting forward from there, 20 December is a Thursday.
- April has 30 days (4 weeks + 2 days), so it has a 5th Monday only if 1 April is a Monday or a Sunday.
- November also has 30 days, so it has a 5th Thursday only if 1 November is a Thursday or a Wednesday.
- Days from 1 April to 1 November = 30 + 31 + 30 + 31 + 31 + 30 + 31 = 214 = 30 weeks + 4 days, so 1 November falls 4 weekdays after 1 April.
- 1 April Monday → 1 November Friday (no 5th Thursday). 1 April Sunday → 1 November Thursday, which fits.
- 1 December = 1 November + 30 days = Thursday + 2 = Saturday.
- 20 December = 1 December + 19 days = Saturday + 5 = Thursday.
Remember · In a 30-day month only the weekdays of the 1st and 2nd occur five times; link months by counting odd days.
Question and answer: UPSC's official GS Paper II (2019, Series A) — paper ↗ · answer key ↗. Explanation: Minimalist IAS, checked 30 Sept 2026 (how we verify). ·