Calendar reasoning – If the 9th day of a month falls on the day immediately before Sunday (i.e., Saturday), on which day of the week does the 1st of that same month fall? Explain the logic clearly and show the backward counting from the 9th to the 1st.

Introduction / Context:
The problem tests basic calendar arithmetic: moving backward or forward by whole weeks and days to determine weekdays for specific dates within the same month.

Given Data / Assumptions:

• The 9th day of an unspecified month is the day preceding Sunday, i.e., Saturday.
• We need the weekday on the 1st of that same month.
• No leap-year or month-length edge case affects weekday differences within a single month when counting fixed day gaps.

Concept / Approach:
Weekdays cycle every 7 days. Moving 7 days backward or forward lands on the same weekday. From the 9th back to the 1st is a gap of 8 days. Subtracting 7 (one full week) reduces the problem to shifting by 1 day backward.

Step-by-Step Solution:
9th = Saturday (given).Days between 9th and 1st = 8.Break 8 as 7 + 1.Move back 7 days: Saturday - 7 = Saturday.Move back 1 more day: Saturday - 1 = Friday.

Verification / Alternative check:
Forward check from the 1st: If 1st were Friday, then 8 days later (1st + 8) is Saturday, matching the 9th being Saturday. Consistent.

Why Other Options Are Wrong:
Saturday would make the 9th and 1st identical weekdays (requires 0 or multiples of 7 difference, not 8). Sunday or Monday are each off by one from the required backward shift.

Common Pitfalls:
Forgetting to reduce 8 by a full week to a 1-day shift, or misreading “preceding Sunday” as “following Sunday.”

Final Answer:
Friday