In ΔPQR, side PQ = 3 cm and side PR = 25 cm. What is the area of ΔPQR ?

Answer: Option B

$$\begin{array}{rl}& \text{Area of }\Delta PQR\\ & =\frac{1}{2}\times QR\times PQ\\ & \text{Given},PQ=3cm\\ & QR=\sqrt{{\left(PR\right)}^2-{\left(PQ\right)}^2}\\ & =\sqrt{{\left(25\right)}^2-3^2}cm\\ & =\sqrt{625-9}cm\\ & =\sqrt{616}cm\\ & =2\sqrt{154}cm\\ & \therefore \text{Area}\text{of}\Delta PQR\\ & =\left(\frac{1}{2}\times 2\sqrt{154}\times 3\right)c{m}^2\\ & =3\sqrt{154}c{m}^2\end{array}$$