rocket science!!!110xff

$r = 0.001 * 0.05;
$p0 = 0.06099;
$rm = 8.706;
$rt = 6180;

# method 1

$a = 2.0 * $r;
$b = $p0 + (6.0 * $r); # $p0 + (2.0 * $r);
$c = -($rt / (280.0 * $rm)) + $p0 + (4.0 * $r);

$delta = sqrt( ($b * $b) - (4.0 * $a * $c) );
$n = 280.0 * (-$b + $delta) / (2.0 * $a);

print "$n\n";

# method 2

$pi = 3.14159265;

$a = $pi * $r;
$b = $p0 + (3.0 * $pi * $r);
$c = -($rt / (280.0 * $rm)) + $p0 + (2.0 * $pi * $r);

$delta = sqrt( ($b * $b) - (4.0 * $a * $c) );
$n = 280.0 * (-$b + $delta) / (2.0 * $a);

print "$n\n";