If the area of a trapezium is 28 cm

Given:

Area of the trapezium $=28 \mathrm{~cm}^{2}$

Length of one of its parallel sides $=6 \mathrm{~cm}$

Altitude $=4 \mathrm{~cm}$

Let the other side be $\mathrm{x} \mathrm{cm} .$

Area of trapezium $=\frac{1}{2} \times($ Sum of the parallel sides $) \times($ Altitude $)$

$\Rightarrow 28=\frac{1}{2} \times(6+\mathrm{x}) \times(4)$

$\Rightarrow 28=2 \times(6+\mathrm{x})$

$\Rightarrow 6+\mathrm{x}=\frac{28}{2}=14$

$\Rightarrow \mathrm{x}=14-6=8 \mathrm{~cm}$

Hence, the length of the other parallel side of the trapezium is $8 \mathrm{~cm}$.