Reasoning Ability - Calendar Problems
A man was born on 10th January 1980. If his 40th birthday was celebrated on Friday, which day was his birth date?
A man was born on 10th January 1980. If his 40th birthday was celebrated on Friday, which day was his birth date?
easy Q13 of 15
Step-by-Step Solution
Step 1: Duration
10 Jan 1980 → 10 Jan 2020 = 40 years.Step 2: Count leap years
Leap years from 1980 to 2019 inclusive: 1980,84,88,92,96,2000,04,08,12,16 → 10 leaps.Step 3: Compute odd days
Ordinary = 30 × 1 = 30; Leap = 10 × 2 = 20; Total = 50 → 50 mod 7 = 1 odd day.Step 4: Back-calculate birth weekday
40th birthday = Friday. Birth weekday = Friday − 1 = Thursday.Final Answer:
Thursday → Option CQuick Check:
Thursday + 1 odd day = Friday ✅
Quick Trick: Count leaps including the starting year if it’s a leap (1980 here).
Common Mistakes:
MISTAKES- Omitting the starting leap year in the leap count.
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