As shown in the figure, the area of trapezoid ABCD is 45 square centimeter, the area of bottom AB is 10 centimeter, the area of triangle doc is 5 square centimeter

As shown in the figure, the area of trapezoid ABCD is 45 square centimeter, the area of bottom AB is 10 centimeter, the area of triangle doc is 5 square centimeter

The length of ad is 45 × 2 ／ 6-10 = 5 (CM), so the area of triangle BCD is 5 × 6 ／ 2 = 15 (cm 2), then the area of triangle BOC is 15-5 = 10 (cm 2), because the area of triangle ABC is 10 × 6 ／ 2 = 30 (cm 2), so the area of triangle AOB is 30-10 = 20 (cm 2). A: the area of triangle AOB is 20 cm 2

As shown in the figure, the area of trapezoid ABCD is 45 square centimeter, the area of bottom AB is 10 centimeter, the area of triangle doc is 5 square centimeter

The length of ad is 45 × 2 ／ 6-10 = 5 (CM), so the area of triangle BCD is 5 × 6 ／ 2 = 15 (cm 2), then the area of triangle BOC is 15-5 = 10 (cm 2), because the area of triangle ABC is 10 × 6 ／ 2 = 30 (cm 2), so the area of triangle AOB is 30-10 = 20 (cm 2). A: the area of triangle AOB is 20 cm 2

Flat quadrilateral ABCD, e and F are the midpoint of AB and BC sides respectively, connecting De, EF and DF. The area of triangle DEF is 7.8 square centimeter. What is the area of flat quadrilateral?

Let the area of parallelogram be s, triangle ade = 1 / 4S, triangle bef = 1 / 8s, triangle DCF = 1 / 4S, that is 5 / 8s + 7.8 = s