IPT calculation (calculate a percentage of a figure)

[mynton]

Hi,

I am fairly new to this so please bare with me.

I have a php page that uses Javascript (I think) to calculate the percentage Insurance Premium Tax (IPT field) of a total.

I have located where the calculation occurs and can see that it take the total of a predefined amount and divides it by 21 to give me the 5% IPT tax. IPT has risen in the UK today to 6% so I need to know what I need to change the 21 to to give me an accurate IPT calculation.

Here's a snippet of the code. Can anyone help please? Is it 17.65?

PHP Code:

////////////////////////////////////////////
// Motor Bike Calculations
////////////////////////////////////////////
$p = 3;
$q = 0;
  while ($p < 6){
  $base_array = mysql_fetch_row($result4);
  // Motor Bikes
  $risk_code = 2;
  $ap = (0 + ($p));

          $ipt_rate = $ipt_main;

  $monthly_total = $pricing_row[$ap];
  // Calculate IPT
  $ipt_percentage = $monthly_total / 21;
  $monthly_ipt = $ipt_percentage;

    $base_cost = $base_array[0] + $dealer_loading;
  $base_final = $base_cost;
  
  $profit = $monthly_total - $base_cost - $monthly_ipt;
  
        $monthly_total = number_format($monthly_total, 2, '.', '');
            $monthly_ipt = number_format($monthly_ipt, 2, '.', '');
                $base_final = number_format($base_final, 2, '.', '');
                    $profit = number_format($profit, 2, '.', '');
                    
  echo '
  <tr align="center" bgcolor="#FFDDFF"> 
    <td>';
if ($p == 3)
{
echo ('');
}
elseif ($p == 4)
{
echo ('UK');
}
elseif ($p == 5)
{
echo ('UK & European');
}
echo '</td>
    <td>
        <input name="';
if ($p == 3)
{
echo ('comprehensive_plus_'.$risk_code);
}
elseif ($p == 4)
{
echo ('comprehensive_'.$risk_code);
}
elseif ($p == 5)
{
echo ('driveline_plus_'.$risk_code);
}


echo '" type="text" value="'.$pricing_row[$ap].'" size="6" maxlength="6" class="smallinfo">
     </td>
    <td>'.$monthly_ipt.'</td>
    <td>'.$base_final.'</td>
    <td>'.$profit.'</td>
  </tr>';
  $q++;
$p++;
} 


[Old Pedant]

Nope. Not a lick of JavaScript in there. That's 100% PHP code.

But you know, the language in use has nothing to do with this. It's just simple arithmetic.

105 / 21 is indeed 5. Simply because, of course, 105 / 5 is 21.


What you need is to solve for x where 106 / x = 6. And simple algebra says x = 106 / 6 or 17.666666667 (that is 17 and 2/3).

So, you almost had the right answer. Just a shade off. You might want to multiply by 6 and then divide by 106 to get as accurate an answer as possible.