Construct a quadrilateral PQRS, in which PQ = 3.5 cm,

Steps of construction:

Step I : Draw QR $=2.5 \mathrm{~cm}$.

Step II : Construct $\angle \mathrm{PQR}=75^{\circ}$ at Q.

Step III : With Q as the centre and radius $3.5 \mathrm{~cm}$, cut off QP $=3.5 \mathrm{~cm}$.

Step IV : Construct $\angle \mathrm{QRS}=120^{\circ}$ at R.

Step V : With R as the centre and radius $4.1 \mathrm{~cm}$, cut off RS $=4.1 \mathrm{~cm}$.

Step VI : Join PS

The quadrilateral so obtained is the required quadrilateral.