src/Number.php
public function is($percentage)
    {
        $number = clone $this;

        if ($percentage instanceof Number) {
            $percentage = $percentage->getValue();
        }

        return $number->bcmul(100)->bcdiv($percentage);
    }
public function is($percentage)
    {
        $number = clone $this;

        if ($percentage instanceof Number) {
            $percentage = $percentage->getValue();
        }

        return $number->bcmul(100)->bcdiv($percentage);
    }
Number IS $percentage of what Number?

@param Number | float $percentage
@return Number