Find the probability of 53 Sundays in an ordinary year.

Explanation

To find the probability of having 53 Sundays in an ordinary year, we can follow these steps:

### Step 1: Understand the number of days in an ordinary year
An ordinary year consists of 365 days.

### Step 2: Calculate the number of weeks in an ordinary year
Since there are 7 days in a week, we can calculate the number of weeks in 365 days:
\[ \text{Number of weeks} = \frac{365}{7} = 52 \text{ weeks} \text{ and } 1 \text{ extra day} \]
So, there are 52 complete weeks and 1 additional day.

### Step 3: Determine the extra day
In an ordinary year, after accounting for the 52 weeks, we have 1 extra day. This extra day can be any day of the week (Monday, Tuesday, Wednesday, Thursday, Friday, Saturday, or Sunday).

### Step 4: Identify the favorable outcome for having 53 Sundays
For there to be 53 Sundays in the year, the extra day must be a Sunday. Since there is only 1 extra day, the only favorable outcome for having 53 Sundays is if that extra day is a Sunday.

### Step 5: Calculate the probability
The total number of possible outcomes for the extra day is 7 (it can be any day of the week). The number of favorable outcomes (having that extra day as a Sunday) is 1. Therefore, the probability \( P \) of having 53 Sundays in an ordinary year is given by:
\[ P(\text{53 Sundays}) = \frac{\text{Number of favorable outcomes}}{\text{Total number of outcomes}} = \frac{1}{7} \]

### Final Answer
Thus, the probability of having 53 Sundays in an ordinary year is:
\[ \frac{1}{7} \]

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