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

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title: 'Problem 1: Multiples of 3 and 5'
---
# Problem 1: Multiples of 3 and 5

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## Problem Explanation
- 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.


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## Solutions

<details><summary>Solution 1 (Click to Show/Hide)</summary>

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


#### Relevant Links
- [Modulo operator](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/Arithmetic_Operators#Remainder_())

</details>