freeCodeCamp/guide/english/certifications/coding-interview-prep/project-euler/problem-1-multiples-of-3-and-5/index.md

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Multiples of 3 and 5

Problem 1: Multiples of 3 and 5

Method:

• We can find if a number is divisble by another number with the help of % modulo operator.
• num1 % num2 returns 0 if there's no remainder while doing num1/num2.
• Starting from i = 3 because that's the first number that's divisble by 3 or 5, we loop through till the number provided.
• If the number is divisible either by 3 or 5, we add that to the variable sum and finally return it.

Solution:

function multiplesOf3and5(number) {
  let sum = 0, i = 3;
  while (i < number){
    if (i % 3 == 0 || i % 5 == 0) sum += i;
    i++;
  }
  return sum;
}

Reference:

• Modulo operator