I solve math problems.

One. fill up a vacancy

1.5.5 square meters = 5 square meters and 50 square decimeters.

2.450 square decimeter =(4) square meter (50) square decimeter

3. The sum of the upper and lower bottoms of a trapezoid is 85 cm, the height is 4 decimeters, and its area is (170) square cm; If the top and bottom are tripled and the height is quadrupled, then its area is (4080) square centimeters.

4. The area of a triangle is 120 cm2, and the area of a parallelogram with the same base and height as this triangle is (240) cm2.

The circumference of the trapezoid is 32 cm, the upper bottom is 12 cm, the lower bottom is 8 cm, and the waist length of the trapezoid is (3.4) cm.

6. The base of parallelogram is 5cm, the height is 2cm, and its area is (10) cm2.

7. The base of the parallelogram is enlarged by four times, the height by two times and the area by eight times.

judge

1. The area of the trapezoid is equal to half the area of the parallelogram. (× )

2. The perimeters of two triangles with the same area must be the same. ( × )

3. The base and height of the parallelogram are enlarged by 5 times, and its area is enlarged by 10 times. (× )

The larger the base of a triangle, the larger the area of the triangle. ( × )

5. The area of parallelogram is larger than that of triangle. (× )

6. The area of the trapezoid is only related to the upper bottom, lower bottom and height of the trapezoid, and has nothing to do with other quantities. ( √ )

3. Fill in the brackets with the serial number of the correct answer.

1. A trapezoid, the upper bottom is 10cm, the lower bottom is 5cm more than the upper bottom, the height is 3cm less than the upper bottom, and the area is (②).

①22.5 cm2 ②87.5 cm2 ③ 150 cm2

2. A pile of steel pipes, 6 at the bottom and 2 at the top, with a difference of 1 between every two adjacent layers. The total number of steel pipes in this pile is (③).

① 12 ② 16 ③20.

3. The base of the triangle is enlarged by 4 times and the height is reduced by 4 times, and the area is (③).

① Magnify by 4 times; ② Reduce by 4 times; (3) remain unchanged.

4. Two parallelograms with equal perimeters (③)

① Equal area ② Same shape ③ Neither of the above two answers is correct.

5. Two triangles (④) can be combined into a parallelogram.

① Equal area ② Arbitrary ③ Same shape ④ Exactly the same.

Seven. application problem

240×(240÷2)×20= 14400000 (tree)

This land can grow14.4 million watermelon seedlings.

90× (90 ÷1.5 )× 0.2 =1080 (kg)

This rice field needs 1080 kg of fertilizer.