Step 1: Understand the given information in the question.

Step 2 : Recall the probability definition.

[Note: Probability of an event happening = Number of ways it can happen / Total number of outcomes.]

Step 3: Calculate the number of ways it can happen

In an ordinary year we have 365 days = 52 weeks + 1 day

So, we have 52 weeks means we have 52 Sundays in every week.

But, we need 53 Sundays in a year for that remaining one day also must be Sunday,

Number of ways it can happen = 1

Step 3: Calculate the Total number of outcomes.

In a week we have 7 days (Sun, Mon, Tue, Wed, Thu, Fri, Saturday.)

So Total number of outcomes. = 7

Step 4: Substitute the values in the formula.

#### Probability that an ordinary year has 53 Sundays = 1/7.