If the first day of the year (other than the leap year) was Sunday, th

If the first day of the year (other than the leap year) was Sunday, then which was the last day of that year ?

Monday
Sunday
Saturday
None of these
This question was previously asked in
UPSC CAPF – 2019
If the first day of a non-leap year is a Sunday, the last day of that year is also a Sunday.
A non-leap year has 365 days. The number of days in a year is 365.
To determine the day of the week for the last day of the year relative to the first day, we can find the number of days modulo 7.
$365 \div 7 = 52$ with a remainder of $1$.
This means 365 days consist of 52 full weeks and 1 additional day.
If the first day is Sunday (Day 1), the day after 52 full weeks (which is Day $1 + 52 \times 7 = 1 + 364 = 365$) will be the same day as the first day.
So, if Day 1 is Sunday, Day 365 is Sunday.