2. The trapezoid has an area of 7.5 and a height of 2.5. Using the trapezoidal area formula, the sum of the upper and lower bottoms of the trapezoid can be 7.5 times 2 and divided by 2.5, which is equal to 6. Depending on the conditions, the divided triangle is an equal-height triangle (the height is the distance between the upper and lower bottoms), and the ratio of the two areas is the ratio of the bottoms. That is, the upper and lower bottoms of trapezoid, the upper bottom; Base = 2: 3, and 6 will be distributed according to the ratio of 2: 3. The top and bottom are 6x2/2+3 = 2.4cm (top and bottom * * *, there are five bottoms), and the bottom is 6-2.4 = 3.6cm. * * There are three knowledge points.
3. This problem is complicated. Note that the total number of medals and the number of gold medals have changed. Only the number of bronze medals has not changed. Take this as the standard quantity and compare the number of gold medals with him. The specific method is as follows: (number of gold medals+1): number of bronze medals = 6: 7 "1" means that the assumed number of gold medals is 6/7 of the number of bronze medals; (Number of gold medals -2): Bronze medals = 3: 4, indicating that the number of gold medals is only three-quarters of the number of bronze medals at this time, and the scoring rate has changed. Look at the figures, which is equivalent to a reduction of three. According to the above analysis, the formula (1+2)/(6/7-3/4)=28 is the unit of 1, that is, the number of bronze medals, and the number of gold medals is six sevenths of his. 28x6/7- 1=23 pieces