A.65 B.60 C.45 D. 15
Example a starts from a certain place in the morning and advances at a constant speed. After a while, B started from the same place and went in the same direction at the same speed. In the morning 10, B walked 6 kilometers, and they went on. When B reached the position where A reached 10 am, A * * walked16.8km.. Q: How many kilometers did B walk at this time?
a . 1 1.4 b . 1.4 c . 1.8d . 5.4
Scientists investigated Pinghai Island. They first captured 30 sparrows for marking, then released them, and then captured 50 sparrows, of which 10 was marked. How many sparrows are there on this island?
150
For example, a batch of parts, if A does it on the first day and B does it on the second day, the number of days to complete it is exactly an integer. If Party B does it on the first day and Party A does it on the second day, it will be done alternately, so there are still 40 pieces to be done after the last time. Assuming that the efficiency ratio between Party A and Party B is 7: 3, how many pieces does Party A make every day?
A.30 B.40 C.70 D. 120
The example pool is equipped with a drainage pipe and several water injection pipes with the same amount of water injection per hour. When the water injection pipe is used for water injection, the drainage pipe simultaneously drains water. If you use 12 water injection pipes to fill the pool in 8 hours, if you use 9 water injection pipes in 24 hours and now use 8 water injection pipes, how many hours can you fill the pool?
A. 12
According to the analysis, there are 2× (120+80)-260 =140 people who have participated in the two subjects. There are 140-75 = 65 girls taking two subjects, so there are 80-65 = 15 girls taking only math and not Chinese.
According to the meaning of the question, when B walks from 10 to A's location 10, the two people walk the same distance, so it is (16.8-6)/2 = 5.4, plus the previous 6 kilometers, a total of * * * has walked 6+5.4 =/kloc-. Choose a.
The proportions before and after the analysis are equal, so 10/50 = 30/x, x = 150, choose a.
The efficiency ratio of analysis A and B is 7: 3, so A is a multiple of 7, and only C meets it.
The typical cattle grazing problem is analyzed. Assuming that the water injection is per hour 1, then the hourly displacement of the drainage pipe is (24× 9- 12× 8)/(24-8) = 7.5, and the original water volume in the pool is (12-7.5 )× 8 = 36.