The area of the trapezium is 1350 cm². The length of the two parallel sides is 30 cm and 40 cm respectively. Calculate the distance between the two parallel sides.

Given, the two parallel sides of the trapezium are 30 cm and 40 cm respectively.

Sum of parallel sides of the trapezium = 30 + 40 = 70 cm.

The area of the trapezium is 1350 cm².

Let the distance (height) between two parallel sides h.

Area of the trapezium = $\frac{1}{2}$x (Sum of parallel sides) x (Height). 

$\begin{array}{rcl}1350& =& \frac{1}{2}\times 70\times \mathrm{h}\end{array}$

$\begin{array}{rcl}\mathrm{h}& =& \frac{1350\times 2}{70}=38.57 \mathrm{cm}\end{array}$

Therefore, the distance between the two parallel sides is 38.57 cm.