Adding Percentage of Number to Itself

Question

I want to add 30.4 percent of $drivervalue to $drivervalue, is it possible to do that as below? I know if I knew what the actual number was going to be I could just put the 30.4 after the 1., but as I wont know what it will be, I am using the variable instead is this a valid syntax?

//example

$drivervalue = 16000000;

$percentdiff = 30.4;

$drivvalue *= 1. $percentdiff;

Answer 1

$drivervalue *= (1 + $percentdiff / 100);