Write a program to check the divisibility of a number by 7 that is passed as a parameter to the user defined f

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Q. Write a program to check the divisibility of a number by 7 that is passed as a parameter to the user defined function.

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Concept understanding — Leap Year Determination

Leap Year Determination

You already know a year is 365 days. But the Earth actually takes about 365.2422 days to orbit the Sun — a little more than 365 days. That extra 0.2422 day (roughly 6 hours) adds up. After 4 years, it becomes almost a full day. So we add an extra day every 4 years to keep the calendar aligned with the seasons. That extra day is February 29, and that year is a leap year.

But if we added a leap day every 4 years without exception, we'd overshoot. Because 0.2422 × 4 = 0.9688 day, not exactly 1 day. So every 4 years we add a bit too much — about 0.0312 day too much. Over centuries, that error accumulates. To fix it, we skip some leap years.

The precise rule

A year is a leap year if:

It is divisible by 4, and
If it is divisible by 100, it must also be divisible by 400.

In other words:

\text{Leap year} \iff ( \text{year} \bmod 4 = 0 ) \land ( \text{year} \bmod 100 \neq 0 \lor \text{year} \bmod 400 = 0 )

Let's break that down.

Step 1: Every year divisible by 4 is a leap year — unless it's a century year.

Step 2: Century years (like 1900, 2000, 2100) are leap years only if they are divisible by 400.

So 2000 was a leap year (divisible by 400). 1900 was not (divisible by 100 but not by 400). 2100 will not be a leap year.

Watch out

A common mistake is to think every year divisible by 4 is a leap year. That's almost true, but the century-year exception is crucial. 1900 was divisible by 4, yet it was not a leap year.

Why this works

The Gregorian calendar (the one we use) was designed to keep the average year length very close to 365.2422 days. The rule gives an average year length of:

\frac{1}{4} - \frac{1}{100} + \frac{1}{400} = 0.2425 \text{ extra days per year}

That's 365.2425 days per year — an error of only 0.0003 day per year, or about one day every 3300 years. Good enough for most purposes.

Quick check

Year	Divisible by 4?	Divisible by 100?	Divisible by 400?	Leap year?
2024	Yes	No	—	Yes
1900	Yes	Yes	No	No
2000	Yes	Yes	Yes	Yes
2100	Yes	Yes	No	No

Tip

For a quick mental check: if the year ends in 00, it's a leap year only if the first two digits are divisible by 4 (e.g., 2000 → 20 ÷ 4 = 5, yes; 1900 → 19 ÷ 4 = 4.75, no).

Final answer: A year is a leap year if it is divisible by 4, except that century years are leap years only if divisible by 400.

The modulus test num % 7 == 0 inside a user-defined function decides divisibility; the number arrives as a parameter.

def divisible_by_7(num):
    if num % 7 == 0:
        print(num, "is divisible by 7")
    else:
        print(num, "is not divisible by 7")

n = int(input("Enter a number: "))
divisible_by_7(n)

Sample runs:

Enter a number: 49
49 is divisible by 7

Enter a number: 30
30 is not divisible by 7

✓Final answer

divisible_by_7(num) prints "divisible by 7" exactly when num % 7 == 0 — true for 49 (remainder 0), false for 30 (remainder 2).

Pass the number as a parameter to a user-defined function and test num % 7 == 0 — remainder zero means divisible; e.g. 49 is divisible by 7, 30 is not.

The idea. Divisibility is a remainder question, so the modulus operator is the whole algorithm: num % 7 is 0 exactly when 7 divides num. The exercise's real point is the function mechanics — the value is read in the main program and handed to the function as a parameter, as the question requires.

def divisible_by_7(num):
    # Report whether num is divisible by 7
    if num % 7 == 0:
        print(num, "is divisible by 7")
    else:
        print(num, "is not divisible by 7")

n = int(input("Enter a number: "))
divisible_by_7(n)          # the number is passed as an argument

Sample runs

Enter a number: 49
49 is divisible by 7

Enter a number: 30
30 is not divisible by 7

How it works

n is read and converted with int(); the call divisible_by_7(n) binds it to the parameter num.
49 % 7 is 0 → the if branch prints the "divisible" message; 30 % 7 is 2 → the else branch runs.
Negative multiples work too: -14 % 7 is 0 in Python, so −14 is correctly reported divisible.

Tip

A variant that returns a Boolean (return num % 7 == 0) is even more reusable — the caller can then count multiples of 7 in a range, filter a list, etc., instead of only printing.

✓Final answer

The function reports divisibility via the remainder test num % 7 == 0 : input 49 \to "49 is divisible by 7"; input 30 \to "30 is not divisible by 7".

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Q.Write a program to check the divisibility of a number by 7 that is passed as a parameter to the user defined function.

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