Question

How to find the sum of all the multiples of 3 or 5 below 10 in C++

Answer 1

#include <iostream>

int main() {
    int sum = 0;
    
    for (int i = 3; i < 10; i++) {
        if (i % 3 == 0 || i % 5 == 0) {
            std::cout << i << "\n";
            sum += i;    
        }
    }
  
    std::cout << "sum = " << sum;
}



/*
run:

3
5
6
9
sum = 23

*/

 

70+ SQL courses for beginners and professionals

Answer 2

#include <iostream>
 
unsigned int Sum(unsigned int n) {
    return (n * (n + 1)) / 2;
}
 
int main() {
    int below10 = 9;
 
    unsigned int sum = 3 * Sum((int)(below10 / 3)) + 5 * Sum((int)(below10 / 5)) - (3 * 5) * Sum((int)(below10 / 15));
     
    std::cout << "sum = " << sum;
}
 
 
 
/*
run:
 
sum = 23
 
*/

 

 

70+ SQL courses for beginners and professionals