A trapezoid has an upper bottom of 8 cm, a lower bottom of 4 cm, and a height of H cm. The area of this trapezoid is () square cm. Two such trapezoids can be used to form a parallelogram with a bottom of () cm and a height of () cm

1／2（8＋4）h

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1. Given that the area of trapezoid is 54 square centimeter, calculate the area of shadow part
2. A trapezoid has an upper base of 8 cm and a lower base of 14 cm. There is a semicircle in the middle with a diameter of 8 cm. The rest are shadows. Calculate the area of shadows
3. The top bottom of trapezoid is 8 cm, the bottom is 6 cm, the area of shadow part is 12 square cm, and the area of blank part is how many square cm? On August 8, 2008, Beijing has successfully held the 29th Olympic Games. There are about 4125.5 million people watching TV in the world. The unit of "ten thousand people" is () ten thousand people, and the mantissa after "hundred million" is () hundred million people If you sell a pen for 100 yuan, you can earn 25%. If you sell it for 120 yuan, how much can you earn
4. The length of a cuboid is 12 cm and the height is 8 cm. The area sum of the four sides of the blank part is 392 square cm. What is the area sum of the shadow part? What is the volume of the cuboid?
5. As shown in the figure on the right, the area of blank part is 24 square centimeters, the area of shadow part a is 5 square centimeters, so the area of shadow part B is () square centimeters?
6. As shown in the figure, two identical right triangles are stacked together to find the area of the shadow part. (unit: cm)
7. It is known that the height of ladder ABCD is h. The two diagonals form angles of 30 degrees and 45 degrees respectively with the bottom to calculate the area of ladder
8. As shown in the figure, it is known that the height of right angled trapezoid is 30cm, ∠ 1 = ∠ 2 = 45 ° and the area of trapezoid ABCD is calculated
9. As shown in the figure, it is known that the height of right angled trapezoid is 30cm, ∠ 1 = ∠ 2 = 45 ° and the area of trapezoid ABCD is calculated
10. In trapezoidal ABCD, AB is parallel to DC, angle a = 60 degrees, angle B = 45 degrees, DC = 2, ad = 4. What is the area of trapezoidal ABCD
11. The height of a trapezoid is 4cm, and the upper and lower bottoms are increased by 8cm. How much is the area increased
12. As shown in the figure, two diagonal lines AC and BD of parallelogram ABCD intersect at point O. proof: Triangle AOB congruent triangle cod
13. Point O is a point in the parallelogram ABCD such that ∠ AOB + ∠ cod = 180 ° proves that ∠ OBC = ∠ ODC
14. In trapezoidal ABCD, AD / / BC, diagonal AC intersects BD at point O, if s △ abd: s △ DBC = 4:9, then △ AOD: △ BOC perimeter ratio
15. In ladder ABCD, ad ‖ BC (AD
16. As shown in the figure, in the quadrilateral ABCD, point E is on BC, ab ‖ De, ∠ B = 78 ° and ∠ C = 60 °, then the degree of ∠ EDC is () A. 42°B. 60°C. 78°D. 80°
17. As shown in the figure, the angle EDC is determined by making an equilateral triangle Abe in square ABCD connecting de and CE=
18. As shown in the figure, given a point E in the square ABCD, and AE = EB = AB, find the degree of ∠ EDC and ∠ ECB
19. In the square ABCD, there is a point E, △ EAB is an equilateral triangle, ∠ CED = several degrees
20. E is a point in the square ABCD, and the triangle Abe is an equilateral triangle, connecting CE and De, then ∠ CBE=____ ,∠DCE=____ ,∠CED=____