If it was Tuesday on December 27, 1986, then what will be the day on 30 July, 2011?

Tuesday

\(\frac{Date + Month code + Century code + Century upper year + Quotient of Upper year/4}{7}\)

\(\frac{27+5+0+86+21}{7}\)

\(\frac{139}{7}\) =  Remainder 6 means Saturday but here Tuesday is given i.e. 4 days before.

We have to find out 30/07/2011

\(\frac{Date + Month code + Century code + Century upper year + Quotient of Upper year/4}{7}\)

\(\frac{30+6+6+11+2}{7}\)

\(\frac{55}{7}\) =  Remainder 6 means Saturday

Therefore, 4 days before Saturday is Tuesday which is the correct answer.

Note:

Code for   

Mon – 1       Tues – 2       Wed – 3                      Thurs – 4     Fri – 5         Sat ­­–6                          Sun – 0

Code for    

Jan – 0         Feb – 3        Mar – 3

Apr – 6        May – 1       June – 4

July – 6        Aug – 2       Sep – 5

Oct – 0         Nov – 3       Dec – 5

Code for        1900 is 0

                    2000 is 6

                    2100 is 4

                    2200 is 2

                    2300 is 0

                    2400 is 6

                    2500 is 4   and  Likewise