Rectangle Area: Calculate When One Side is 6cm and Another is 40% Longer

Let's begin by calculating side AB:

$AB=BC+40\%$

$AB=6+40\%$

$AB=6+\frac{40}{100}\times6$

$AB=6+\frac{4}{10}\times6$

$AB=6+\frac{4\times6}{10}=6+\frac{24}{10}=6+2.4=8.4$

We can now calculate the area of the rectangle by multiplying the length by the width:

$8.4\times6=50.4$