C Exercises: Find the sum of all the multiples of 3 or 7 below 100

Last update on May 27 2022 12:24:23 (UTC/GMT +8 hours)

C Programming Practice: Exercise-17 with Solution

The natural numbers below 10 that are multiples of 3 or 7 are 3, 7, 6 and 9. The sum of these multiples is 25.
Write a C programming to find the sum of all the multiples of 3 or 7 below 100.

C Code:

#include <stdio.h>
int main(void)
{
  int sum3 = 0, sum7 = 0, sum21 = 0;
  int i;
  for (i = 0; i < 100; i++) {
    if (i % 3 == 0) {
      sum3 += i;
    }
    if (i % 7 == 0) {
      sum7 += i;
    }
    if (i % 21 == 0) {
      sum21 += i;
    }
  }
  printf("%d\n", sum3 + sum7 - sum21);
  return 0;
}

Sample Output:

Flowchart:

C Programming Code Editor:

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Previous: Write a C programming to find the length of the longest valid (correct-formed) parentheses substring of a given string.
Next: Write a C programming to find the sum of the even-valued terms from the terms in the Fibonacci sequence whose values do not exceed one million.

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C Programming: Tips of the Day

Static variable inside of a function in C

The scope of variable is where the variable name can be seen. Here, x is visible only inside function foo().

The lifetime of a variable is the period over which it exists. If x were defined without the keyword static, the lifetime would be from the entry into foo() to the return from foo(); so it would be re-initialized to 5 on every call.

The keyword static acts to extend the lifetime of a variable to the lifetime of the programme; e.g. initialization occurs once and once only and then the variable retains its value - whatever it has come to be - over all future calls to foo().

Ref : https://bit.ly/3fOq7XP