- Spoiler Alert -
If you have any interest in solving any of these problems at Project Euler, quit reading this post and immediately pull up your programming editor of choice and have at it.
Problem 1: 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.
$result = 0
for($i = 0; $i -lt 1000;$i++)
if ($i % 3 -eq 0 -or $i % 5 -eq 0)
$result += $i;