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?
Fifth Monday of April can be possible only on 29th or 30th of April.
Similarly, fifth Thursday of November can be possible only on 29th or 30th November.
Number of odd days between Monday and Thursday = 3.
Number of odd days between birthdays of two children = 3.
If the birth of first child is on 30th April,
number of odd days = 31 + 30 + 31 + 31 + 30 + 31 + 29 = 213
= 3 odd days
The birth of second child is on 29th November.
Number of odd days between 29th November and 20th December = 21 = 0 odd day.
Therefore, birthday of third child is on Thursday.
The correct option is B.