# Project Euler: #1 - Multiples of 3 or 5

### Problem

If we list all the natural numbers below 10 that are multiples of 3 or 5, we get 3, 5, 6 and 9. The sum of these multiples is 23.

Find the sum of all the multiples of 3 or 5 below 1000.

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### Problem Description

This is a more straightforward problem.

The natural numbers below 10 would be **1,2,3,4,5,6,7,8 and 9** (Since it is below 10, 10 is exclusive)

And those multiples of 3 are **3, 6 and 9**

And multiples of 5 would be **5**.

So now, the sum of all those multiples would be,

3 + 6 + 9 + 5 = 23.

So now, we want to find the sum of all the multiples of 3 and 5 below 1000 (1000 is exclusive)

---

### Approach

My approach is to get all the multiples of 3 or 5 in an array - `multiples` and then use `Array.prototype.reduce()` function to calculate the sum of all items in that array `multiples`

For my solution, the time taken is between 0.11ms and 0.14ms.

Another approach can be to add the multiples directly to a variable, instead of pushing to an array. Inside the `if`, we can use `sum += i` and print the sum which is our result.

As I said before, there is more than one approach to each problem!

---

### Solution

```javascript
const multiples = [];

for (let i = 1; i < 1000; i++) {
    if (i % 3 === 0 || i % 5 === 0) {
        multiples.push(i);
    }
}

console.time("p#1");
console.log(multiples.reduce((acc, curVal) => acc + curVal));
console.timeEnd("p#1");
```

![Project Euler: #1 Solution Answer](https://cdn.hashnode.com/res/hashnode/image/upload/v1672049332926/8cc46463-a941-4f6b-865a-6927bba581c8.png align="left")

The GitHub repo for this problem is found at [01](https://github.com/sansk/project-euler-solutions-javascript/tree/main/01)

If you have another solution, please leave it in the comments below.

For the other Project Euler Solutions, please follow the series [Project Euler Solutions in JS.](https://theintrovertcoder.hashnode.dev/series/project-euler)

Thank you!