Eshan's birthday in a certain year falls on Friday, 10th March. In the same year, Shlok was born on 25th September. On which day of the week does Shlok's birthday fall in that year?

Introduction / Context:
This question involves two dates within the same year, one in March and one in September. You are given the weekday for Eshan's birthday and must deduce the weekday for Shlok's birthday. It is a calendar-based reasoning problem that requires accurate counting of days across several months and then translating that into a weekday shift.

Given Data / Assumptions:

• Eshan's birthday: Friday, 10th March in some year.
• Shlok's birthday: 25th September of the same year.
• Standard month lengths:
  • March: 31 days
  • April: 30 days
  • May: 31 days
  • June: 30 days
  • July: 31 days
  • August: 31 days
  • September: 30 days
• Both dates are after February, so leap year vs non-leap year does not change the relative difference.

Concept / Approach:
We count the number of days between 10th March and 25th September, then reduce that count modulo 7 to determine how many days forward we move from Friday. This difference tells us the weekday for 25th September in the same year.

Step-by-Step Solution:
Step 1: Days remaining in March after 10th March: 31 - 10 = 21 days (11th to 31st). Step 2: Full months from April to August: April: 30 days, May: 31 days, June: 30 days, July: 31 days, August: 31 days. Step 3: Total days for April to August inclusive = 30 + 31 + 30 + 31 + 31 = 153 days. Step 4: Days in September up to 25th September = 25 days. Step 5: Total days between 10th March and 25th September = 21 (March) + 153 (April to August) + 25 (September) = 199 days. Step 6: Compute 199 mod 7. Since 7 * 28 = 196, remainder is 199 - 196 = 3. Step 7: A remainder of 3 means a 3-day forward shift from Friday. Step 8: Starting at Friday: Saturday (1), Sunday (2), Monday (3). Step 9: Therefore, Shlok's birthday on 25th September falls on a Monday.

Verification / Alternative check:
199 days can be viewed as 28 full weeks (196 days) plus 3 extra days. Full weeks do not alter the weekday; only the remaining 3 days matter. From Friday, three steps forward indeed land on Monday. This result is independent of the specific year chosen (as long as month lengths are standard), confirming the answer.

Why Other Options Are Wrong:
Wednesday would imply a 5-day shift from Friday, Friday a 0-day shift, Thursday a 6-day shift, and Tuesday a 4-day shift. None of these match the required 3-day shift produced by 199 days. Only Monday matches the computed difference modulo 7.

Common Pitfalls:
Miscounting days in the months or skipping one of the months in the middle often leads to incorrect totals. Another error is to mix up whether to include or exclude the starting date when counting. A consistent method is to count days after the starting date until reaching the target date and then apply modulo 7 to convert that total into weekday movement.

Final Answer:
Shlok's birthday in that year falls on Monday.