Question 20
The diagram shows quadrilateral $ABCD$ with $AB=AD=a$ cm and $BC=CD=b$ cm, where $a>b$ and both are whole numbers. Its area is 385 cm$^2$. Find its smallest perimeter, in cm. Source note: the diagram contains no right-angle marks; the source key appears to assume right angles. This discrepancy is analysed in the solution.
