The equation which provides the multiplication of the means and the extremes in the equation provided above can be obtained through cross multiplication of the two ratios or proportion.
(7.2 / 9.6) = (21.6 / 28.8)
L. H. S = R. H. S
(numerator of L. H. S * denominator of R. H. S) = (denominator of L. H. S * numerator of R. H. S)