ABCD is a parallelogram, $\text{AE}\perp \text{DC}$  and $\text{CF}\perp \text{AD}$ . If

$AB=18cm, AE=4cm$  and $\text{CF}=6cm$ , then $AD=$

                                              

Given $AB=CD=18cm$

$AE=4cm$

$CF=6cm$

Area of parallelogram $\text{ABCD = base×corresponding}\text{height}$

$=CD\times AE$  (or)$AD\times CF$

$CD\times AE=AD\times CF$

From the figure $18\times 4=AD\times 6$

$AD=\frac{18\times 4}{6}=12cm$

$AD=12cm$