What is the area of this trapezoidal garden? (All measurements are in cm)

The trapezium has a top side of 15 cm, slanting sides of 13 cm and a height of 12 cm. Each slanting side, with the height, forms a right triangle whose base is √(13² − 12²) = 5 cm, so the bottom side = 5 + 15 + 5 = 25 cm. Area = ½ × (15 + 25) × 12 = 240 sq. cm.