There are two groups of numbers, the average number of the first group is 12.8, the average number of the second group is 10.2, and the total average number of these two groups is 12.02, then the ratio of the number of the first group to the number of the second group is () A. 90:39b. 30:13c. 91:39d

Take the total number as "1", let the first group be x, then: 12.8x + 10.2 × (1-x) = 12.02 & nbsp; & nbsp; 12.8x + 10.2-10.2x = 12.02 & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & 2.6x = 1.82 & nbsp; & nbsp; & nbsp

RELATED INFORMATIONS

1. Average application Last year, Xiaoying's food expenditure was 3600 yuan, education expenditure was 1200 yuan, and other expenditure was 7200 yuan. This year, Xiaoying's food expenditure decreased by 9%, education expenditure increased by 70%, and other expenditure decreased by 6% calculation: (1) The total expenditure of Xiaoying family last year (2) How much has Xiaoying family increased and decreased this year? (3) Xiaoying's total expenditure this year (4) What is the percentage increase of Xiaoying's total expenditure this year compared with that of last year?
2. Average application 2 1. After reading a book for 37 days, Xiao Jun still had 1 / 3 of the original book. After that, he read 12 pages a day and another 5 days, just finished. How many pages does he read every day? 2. Someone goes up the mountain at the speed of 3 kilometers per hour, and goes back along the original road at the speed of 6 kilometers per hour when he goes down the mountain? 3. A tractor plows two identical plots of land. The first plot plows 20 mu per day on average, and the second plot plows 16 mu per day on average. After all the two plots are plowed, how many mu per day does the Tractor Plow? 4. There are four numbers. From the second number, each number is three more than the previous one. The average of these four numbers is 24.5. What is the largest of these four numbers? five
3. Xiaogang's family spent 500 yuan on meals, 200 yuan on education and 500 yuan on other expenses last month. This month, the three expenses of Xiaogang's family increased by 10%, 30% and 5% respectively. What's the percentage increase of Xiaogang's total expenses this month compared with last month?
4. An average problem Wang Hua's average score in six subjects, such as Chinese and mathematics, was 93 points last semester. After that, he took a special course. The average score of the special course was 3 points higher than that of the seven subjects. How many points did Wang Hua get in his special course? Use arithmetic to explain the process of solving problems (do not use equations or equations to solve problems)
5. Integral calculation in grade one of junior high school M + n power of X (n power of 3x, n power of Y) divided by (- n power of 2x, n power of Y)
6. Integral calculation in Volume 1 of junior high school
7. Integral addition and subtraction + answers, 60 questions,
8. The addition and subtraction of integral in the first day of junior high school
9. 100 questions on the addition and subtraction of integral in the first day of junior high school There should be numbers, letters, equations
10. Simplified evaluation: (1) . 1 / 2x + (- 3 / 2x + 1 / 3Y ^ 2) - (2x-2 / 3Y ^ 2), where x = - 1 / 3, y = 2 / 3 (2) . [(XY + 2) (XY-2) - 2x ^ 2Y ^ 2 + 4] / (XY), where x = 10, y = - 1 / 25 (3) . x (x + 2Y) - (x + 1) ^ 2 + 2x, where x = 1 / 25, y = - 25
11. Practical problems of grade 6 1. The number a is 23 / 7, 3 more than the number B. the number C is 7 / 10 of the number B. what is the number C 2. The original 15 kg of monosodium glutamate in the hotel was used up by 1 / 5 in the first week and the remaining 1 / 3 in the second week. How many kg of monosodium glutamate should we buy to be 2 kg more than the original one
12. 20 sixth grade score calculation questions, 4 scores
13. Practical problems of grade 6 1. The fruit shop wholesales a batch of oranges and pears at a total price of 1700 yuan. When the oranges are sold at 26% profit and the pears are sold at 11% profit, the total price is 2007 yuan. How much is the purchase price of these oranges? 2. The department store sells a batch of clothes at 60 yuan per piece. When five eighths of the clothes are sold, the department store will make a profit of 200 yuan after recovering all the costs. When the rest of the clothes are sold, it will make a profit of 1800 yuan. What is the cost of this batch of clothes? 3. At present, the concentration of 10% brine is 20 kg. How many kg of 30% brine can be added to obtain 22% brine? 4. For a TV set, the market will add 35% to the purchase price, and then sell it at a 10% discount. The price of each TV set is 50 yuan, so that each TV set can make a profit of 208 yuan. How much is the purchase price of this TV set?
14. The basic quantitative relationship of practical questions of fractions There are three one two three
15. For a batch of parts, it takes 8 hours for Party A to produce them alone. Now, after Party A has done it for 2 hours, Party B has joined in the work, and it takes 4 hours for them to complete the task. It takes Party B to produce these parts alone___ Hours
16. Application questions, quick The total weight of two baskets of vegetables is 84 kg. Take 20% of them out of basket a and put them into basket B. take 2 kg out of basket B and put them into basket a. the weight of the two baskets is exactly the same. How many kg are the total weight of the two baskets?
17. （1998/1-1）（1997/1-1）（1996/1-1）...（1001/1-1）（1000/1-1） Wrong, the numerator is 1, the denominator is 1998, everything else is
18. Mixed operation of rational numbers, The interest tax of a certain one-year fixed deposit with an interest rate of 20% (for example: deposit 100 yuan for one-year period, and the calculation formula of the income interest of the due depositor after tax is 100 * 2.25% - 100 * 2.25% * 20%). If a depositor has a one-year fixed deposit with an interest rate of 450 yuan after tax, how much is the deposit?
19. Please write a rational number mixed operation problem and write the calculation process. The problem should meet the following conditions at the same time: 1. It must contain five operations: addition, subtraction, multiplication, division and power 2. Divisor must be a fraction 3. The base of a power operation must be a negative fraction 4. The result is equal to 2010
20. Mixed operation of rational numbers, 1. (simple method) - 99 and 18 / 17 * (- 9) 2、-1²-【10/7+（-12）/6】²*（-3/4）³