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Introduction

In this tutorial, you will learn how to write a C program to check if a number is divisible by 3 or not using if-else Statement in C. From mathematics, We know that if the sum of a given number is divisible by 3 then the number will be divisible by 3. We can check the divisibility by 3 using the % operator. In this article, we will see using the % operator. Also In this article, we have covered the algorithms, explanations, and examples to solve this problem.

Problem Statement

Write a C program that reads a number from the user. And checks whether it is divisible by 3 or not using the “if-else” statement. The program should give the output whether the number is divisible by 3 or not.

Example

Enter a number: 15
The number 15 is divisible by 3.

In the above example, we can see that the given input is 15. If we add 1 and 5 it will become 6. As 6 is divisible by 3, 15 will be also divisible by 6.

We can directly check the input number by applying % Operator. We need not to perform the summation of the input number digits.

Algorithm

1. Start the program.
2. Read a number from the user and store it in a variable, let’s say num.
3. Use the modulo operator (%) to calculate the remainder when num is divided by 3.
4. If the remainder is equal to 0, display a message indicating that the number is divisible by 3.
5. Otherwise, display a message indicating that the number is not divisible by 3.
6. End the program.

Program to Check a GivenNumber is Divisible by 3 or not

#include <stdio.h>
int main() {
    int num;
    printf("Enter a number: ");
    scanf("%d", &num);
    if (num % 3 == 0) {
        printf("The number %d is divisible by 3.\n", num);
    } else {
        printf("The number %d is not divisible by 3.\n", num);
    }
    return 0;
}

Output 1

Enter a number: 15
The number 15 is divisible by 3

Output 2

Enter a number: 14
The number 14 is not divisible by 3

I hope this program is clear to you all.