CBSEJEEClass 11
What is the probability that an ordinary year has 53 Sundays?
Answer
The probability that an ordinary (non-leap) year has 53 Sundays is 1/7.
The working
Count the days
An ordinary year has 365 days, which is 52 complete weeks plus 1 extra day.
The 52 weeks
The 52 complete weeks already give exactly 52 Sundays, so a 53rd Sunday depends only on the 1 remaining day.
The extra day
This one leftover day is equally likely to be any of the 7 days: Sunday, Monday, ..., Saturday.
Find probability
There is only 1 favourable case (the extra day being a Sunday) out of 7, so P(53 Sundays) = 1/7.
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