Answer:
251.2 cm²
Step-by-step explanation:
The quadrilateral is formed by the composition of two right triangles
The area of a right triangle is (1/2)bh where b is the base and h is the height
Right ΔABD has base AB = 18.4cm and height AD = 11cm
The area of this triangle = (1/2) 18.4 x 11 = 101.2 cm²
Right Δ BCD has base BC = 20cm and height CD = 15cm
Area of this triangle = (1/2) x 20 x 15 = 150 cm²
Area of quadrilateral ABCD = area of ΔABD + area of ΔBCD
= 101.2 + 150 = 251.2 cm²
