gistfile1.pl

$chance = 30;

$total = 0;
$times  = 0;
for ($i=0; $i<500000; $i++) {
	$seen = 0;
	for ($t = 0; $t<15; $t++) {
		$roll = int(rand(100) + 1);
		if ($roll < $chance) { $seen++; }
		elsif (($t == 4 && $seen == 0) || ($t == 9 && $seen == 1) || ($t == 14 && $seen == 2)) { $seen++ ; }
		if ($seen == 3) {
			$total += $t;
			$times++;
			last;
		}
	}
}

printf("%d tries = avg %.2f", $times, $total / $times) . "\n";