Mishti's birthday in a certain year falls on Thursday, 27th April. In the same year, Aradhya was born on 20th October. On which day of the week does Aradhya's birthday fall in that year?

Introduction / Context:
This question again relates two birthdays within the same year. You are given the weekday of Mishti's birthday and must find the weekday of Aradhya's birthday. The dates extend from April to October, so several intervening months must be handled carefully. The solution relies on counting total days between the two dates and then applying modulo 7 to get the weekday shift.

Given Data / Assumptions:

• Mishti's birthday: Thursday, 27th April.
• Aradhya's birthday: 20th October of the same year.
• Standard month lengths:
  • April: 30 days
  • May: 31 days
  • June: 30 days
  • July: 31 days
  • August: 31 days
  • September: 30 days
  • October: 31 days
• All dates are after February, so leap year vs non-leap year does not affect the relative difference for these months.

Concept / Approach:
We calculate the number of days from 27th April to 20th October and then reduce that number modulo 7 to find how many days ahead of Thursday Aradhya's birthday falls. This shift directly gives the weekday of 20th October in that same year.

Step-by-Step Solution:
Step 1: Days remaining in April after 27th April: 30 - 27 = 3 days (28th, 29th, 30th). Step 2: Full months from May to September: May: 31 days, June: 30 days, July: 31 days, August: 31 days, September: 30 days. Step 3: Total for these full months = 31 + 30 + 31 + 31 + 30 = 153 days. Step 4: Days in October up to 20th October = 20 days. Step 5: Total days between 27th April and 20th October = 3 (April) + 153 (May to September) + 20 (October) = 176 days. Step 6: Compute 176 mod 7. Since 7 * 25 = 175, remainder is 176 - 175 = 1. Step 7: A remainder of 1 means we move 1 day forward from Thursday. Step 8: Starting from Thursday, moving one day ahead brings us to Friday. Step 9: Therefore, Aradhya's birthday on 20th October falls on a Friday.

Verification / Alternative check:
We can interpret 176 days as 25 full weeks (175 days) plus 1 extra day. Twenty-five full weeks bring us back to Thursday, and the additional day shifts us to Friday. Since every step used standard month lengths and both dates fall after February, this result holds regardless of leap-year status.

Why Other Options Are Wrong:
Wednesday would be one day before Thursday, not one day after. Saturday and Sunday correspond to shifts of 2 and 3 days from Thursday, respectively, while another Thursday would imply zero shift. All these contradict the single-day shift produced by the 176-day interval, so they are incorrect.

Common Pitfalls:
As with many calendar questions, miscounting the days in one of the months or forgetting to include the correct number of days in the starting or ending month can lead to an incorrect total. Another pitfall is forgetting to apply modulo 7, leading to confusion when working with larger day counts. A systematic approach—month-by-month counting followed by modulo 7 reduction—helps avoid these errors.

Final Answer:
Aradhya's birthday in that year falls on Friday.