Question

bob was born on 14 january 1992 (tuesday), what day of the week will it be on his 18th birthday?​

Answer 1

Answer:

Thursday 2010/1/14

Answer 2

Given,

Mr. Bob was born on the 14th of January 1992 and the said day was Tuesday.

To Find,

Which day of the week, will it be on the 18th birthday of Mr.Bob.

Solution,

From the given data, it can be deduced that the year of birth of Mr.Bob was a leap year.

A leap year is one in which, there are 366 days, instead of 365 days in the normal year.

In the leap year, the month of February will have 29 days, instead of 28 days, as in a normal year.

Mr.Bob will celebrate his 18th birthday in the year 2010.

The number of leap years between Mr.Bob's 18th Birthday = $\frac{18}{4}$ = $4.5$

And since 1992 is also a leap year, the total leap years = 5

Thus the total number of days between his date of Birth and his 18th Birthday = 18×365+5 =  6575

Thus the number of weeks = $\frac{6575}{7}$=939.28, which is 939 weeks and 2 days.

Thus 16th January 2010 will be Tuesday and thus 18th January will be Thursday.

Henceforth, the 18th birthday of Mr.Bob is Thursday of the week.