Manju correctly remembers that his father's birthday is not after eighteenth of April. His sister correctly remembers that their father's birthday is before twentieth but after seventeenth of April. On which day in April was definitely their father's birthday?
Seventeenth or Eighteenth.
According to Manju birthday = 16, 17, 18. According to Manju's sister birthday = 18, 19. Common day 18th April.