Procent udregner

<h2>Procent udregner<h2>
<form action="" method="post">
<input type="text" name="procent" value="30" /><br />
<input type="text" name="tal" value="6" /><br />
<input type="submit" value="Udregn" />
</form>
<?php
if (isset($_POST['tal'])) {
echo '<h3>Facit</h3>';
$procent = $_POST['procent'];
$tal = $_POST['tal'];
echo $procent / 100 * $tal;
}
?>