According to the Project Euler website, “Project Euler is a series of challenging mathematical/computer programming problems…”

Always a fan of puzzles, I have decided to share my attempts and solutions here.

**Note:** If you are trying to solve Problem #1 for yourself, **DO NOT READ AHEAD!**

### Problem #1

#### Problem Description

Problem #1 entails finding the sum of all of the multiples of 3 or 5 under 1000.

#### Solution

This one was rather simple. The modulo mathematical operator (%) finds the remainder of one number divided by another. If the remainder is 0 (i.e. if `x % y = 0`), then `x` is a multiple of `y`.

Therefore, the task is simple: count from 1 to 999 (we want the numbers **below** 100, remember), check if `n % 3 = 0` or `n % 5 = 0`. If either is a match, we add that to the running total.

#### Code (PHP)

1 2 3 4 5 6 7 | $x = 0; for ($i = 1; $i < 1000; $i++) { if ($i % 3 == 0 || $i % 5 == 0) { $x += $i; } } echo $x; |

**Total Sum:** 233168

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