Add all of them up and divide by the total number.
$numbers = array(10,18,84,52,12,36);
$sum=0;
for ($i = 0; $i<count($numbers); $i++) {
$sum += $numbers[$i];
}
$average = $sum / count($numbers);
echo $average;
That should output some rounding variation of : 35.3
Denise