public function daleChallReadabilityScore($strText = false)
    {
        $strText = $this->setText($strText);

        $score = Maths::bcCalc(
            Maths::bcCalc(
                0.1579,
                '*',
                Maths::bcCalc(
                    100,
                    '*',
                    Maths::bcCalc(
                        $this->daleChallDifficultWordCount($strText),
                        '/',
                        Text::wordCount($strText, $this->strEncoding)
                    )
                )
            ),
            '+',
            Maths::bcCalc(
                0.0496,
                '*',
                Maths::bcCalc(
                    Text::wordCount($strText, $this->strEncoding),
                    '/',
                    Text::sentenceCount($strText, $this->strEncoding)
                )
            )
        );

        if ($this->normalise) {
            return Maths::normaliseScore($score, 0, 10, $this->dps);
        } else {
            return Maths::bcCalc($score, '+', 0, true, $this->dps);
        }
    }