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Problem 1

Solved on 2/26/2008

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.

for($ic = 3; $ic< 1000; $ic++){
  if(($ic % 3) == 0 || ($ic % 5) == 0) $answer += $ic;
}
$answer = 233,168