In a 30-day month that begins on a Saturday, every Sunday and the second and fourth Saturdays are holidays. How many working days are there in that month?

Introduction / Context:
This question reflects a common office and bank holiday pattern: all Sundays plus the second and fourth Saturdays are holidays. You are asked to apply this pattern to a specific 30-day month that begins on a Saturday and then count the remaining working days. This type of problem is frequently seen in aptitude exams.

Given Data / Assumptions:

• The month has 30 days.
• The 1st day of the month is Saturday.
• Every Sunday is a holiday.
• The second and fourth Saturdays are holidays.
• All other days are working days.

Concept / Approach:
We first determine the dates of all Saturdays and Sundays in the month using the given starting weekday. Then we mark which Saturdays are the second and fourth. Once all holiday dates are identified, we subtract their count from the total number of days in the month to obtain the number of working days.

Step-by-Step Solution:
Step 1: Since 1st is Saturday, the weekdays for the first few days are: 1 Sat, 2 Sun, 3 Mon, 4 Tue, 5 Wed, 6 Thu, 7 Fri.Step 2: Continuing this pattern, Saturdays fall on dates: 1, 8, 15, 22 and 29.Step 3: Sundays fall on dates: 2, 9, 16, 23 and 30.Step 4: The second Saturday is the one on the 8th, and the fourth Saturday is the one on the 22nd.Step 5: Holiday dates are therefore: Saturdays 8 and 22, plus all Sundays 2, 9, 16, 23 and 30.Step 6: Count the holidays: there are 2 special Saturdays + 5 Sundays = 7 holidays in total.Step 7: Total days in the month = 30. Working days = 30 − 7 = 23.

Verification / Alternative check:
A quick consistency check: there are 5 Saturdays and 5 Sundays in a 30-day month starting on Saturday. If only 2 of the 5 Saturdays (second and fourth) are holidays while all 5 Sundays are holidays, holiday count is 2 + 5 = 7. Subtracting from 30 again confirms there are 23 working days.

Why Other Options Are Wrong:
25 or 24 working days would imply fewer than 7 holidays, contradicting the second-and-fourth-Saturday plus all-Sunday rule. 22 or 21 working days would require more holidays than the pattern allows. Only 23 matches the correct counting.

Common Pitfalls:

• Treating all Saturdays as holidays instead of only the second and fourth Saturdays.
• Miscounting the positions of Saturdays and Sundays due to an off-by-one error from the starting day.
• Forgetting that the month has only 30 days and accidentally including a 31st day.

Final Answer:
The month has 23 working days.