1, in the wheat experimental field with the same plot area, the original variety was used in the first plot and the new variety was used in the second plot, and 9000Kg and 15000Kg of wheat were harvested respectively. It is known that the yield per hectare of the first plot is 3000 kilograms less than that of the second plot, so the yield per hectare of this experimental field is calculated separately.

2. There are two expressways from A to B: one is an ordinary expressway with a total length of 600Km, and the other is an expressway with a total length of 480Km. The average speed of buses traveling on expressways is 45Km faster than that of ordinary highways, and the time required from expressways to the second place is half that of ordinary highways to the second place. Find the time required for the bus to travel from the expressway to the second place.

3. the distance from a to b is 15km. A rides a bike from a to b first. After 40 minutes, B rides from A and arrives at the same time. Given that the speed of B is three times that of A, find the speed of two cars.

4. A tractor A plowed half of a piece of land in 4 days, and a tractor B plowed the other half in 1 day. B How many days does it take a tractor to plow the field alone?

5. The time required for A to manufacture 90 parts is the same as that required for B to manufacture 120 parts. It is known that A and B manufacture 35 machine parts per hour. Find out how many parts A and B produce per hour.

A factory made a profit of 250,000 yuan last year. According to the plan, this profit should be 20% of the total profit last year and this year. What should be the profit this year?

7. A farm has 400 hectares of paddy fields and 65,438+050 hectares of dry fields. In order to increase the output per unit area, it is planned to change some dry fields into paddy fields. After the change, dry land is required to account for 10% of paddy field. How many hectares of dry land should be changed into paddy fields?

Our troops intercepted the enemy at the bridge. When we set out, the enemy was 24 kilometers away from the bridge, and our army was 30 kilometers away from the bridge. The speed of our army's urgent March is 1.5 times that of the enemy. As a result, we arrived 48 minutes earlier than the enemy, so we asked our army to speed up.

9. It takes the same time for a ship to sail 80km downstream and 60km upstream. Given the current speed of 3 km/h, find the ship speed in still water.

10. When a middle school travels to a place 15 kilometers away from the school, the advance team and the brigade set out at the same time, with the speed of 1.2 times that of the brigade, and arrived at the destination half an hour in advance to make preparations. What's the speed of the advance team and the brigade?

1 1. A coal mine now mines an average of 330 tons more per day than originally planned. It is known that the time required to mine 33,000 tons of coal now is the same as the time required to mine 23 100 tons of coal originally planned. How many tons of coal are mined on average every day?

12, a certain unit of our army went to a place 30 kilometers away from the station to perform tasks. Due to the change of circumstances, the speed of the emergency March must be 1.5 times of the original plan, so as to arrive two hours earlier as required, so as to achieve the speed of the emergency March.

13. The marked price of a commodity is higher than the cost 10%. When the commodity is sold at a reduced price, the price reduction shall not exceed d% in order not to lose money. Please use p for d. ..

14, someone swam along a river for l meters and then swam back to the starting point against the current. Suppose the swimming speed of this person in still water is xm/s and the current speed is nm/s, and ask him the time t required for a round trip.

(1) Xiao Fang swims in a river with a current speed of 0.01m/s. Her swimming speed in still water is 0.39m/s, and the distance from the starting point to a fixed boat by the river is 60m. Ask her how long it takes to get to the ship from the starting point and back.

(2) Zhiyong is a neighbor of Xiao Fang and likes swimming in the river. He remembers that it took about 2.5 minutes to go back and forth from the starting point to the willow tree. Assuming that the speed at that time was 0.0 15m/s and Zhiyong's swimming speed in still water was 0.585m/s, what was the distance from the starting point to the willow?

15. The buyer of a shopping mall predicted that a shirt in this season would sell well in the market, so he bought it with 80 thousand yuan. After it was put on the market, it was really in short supply. The mall bought the second batch of this shirt for176,000, which is twice as much as the first batch, but the unit price is 4 yuan. When this shirt was sold in the shopping mall, there was 65438+ for each 58 yuan.