A trapezoid, the ratio of the upper bottom to the lower bottom is 4: 9. If the bottom surface is reduced by 15cm, it becomes a square, and the ratio of the square area to the original area is ().

Schools should choose two programs from the three chorus programs and two dance programs of the art festival, and there are () different ways to choose.

A rectangle with a length of 3 cm and a width of 2 cm rotates rapidly along its width direction, forming a (). Its surface area is () and its volume is () [take 3].

There is a bag with three yellow balls and two white balls hidden. Adding () black balls will make the possibility of encountering black balls reach 50%.

On the map with the scale of 1: 100000, car A and car B drive from two places at the same time. This road is 900 kilometers long, and the speed ratio between Party A and Party B is 2: 3. They met six hours after driving. Therefore, the speed of Party A is ().

The second big problem is the application problem.

1. A piece of plasticine is first kneaded into a cylinder with a diameter of 3 cm and a height of 6 cm, and then kneaded into a cone with a bottom area of 6.28. What is the height of the cone?

2. The students went for an outing and walked 80% of the whole journey, just arriving at the Children's Palace. On their way back, they walked 25% of the whole journey and passed the Children's Palace by 0.3 km. How many kilometers is it from the outing to the Children's Palace?

3. When donating money to Yushu, we organized a benefit performance, and sold tickets 1000, adult 10 yuan, and student tickets of 6932 yuan to 5 yuan. How many student tickets have been sold? (two methods)

The third question is that I can do calculations.

1. Solve the equation

18x- 15x = 36 5:3 =( 1.2+x):8