A simple method of 1500-2000 + 1999-1998 + 1997 -. - 4 + 3-2 + 1

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• 1. (1) We know that 1 + 3 = 4 = 2, 1 + 3 + 5 = 9 = 3, 1 + 3 + 5 + 7 + 9 = 25 = 5 Following the example above, calculate 1 + 3 + 5 + 7 + +99=? According to the above rule, please use the natural number n (n is greater than or equal to 1) to express the general rule (2) Look at the following equation. Please use the equation about n to show the law you found 9-1=8,16-4=12,25-9=16,36-16=20…… (3) Given that the square of (2x-1) = the square of AX + BX + C, find the value of a + C, 4A + B + 4C
• 2. How to fill in 2, 3, 4, 5, 6, 7, 8, 9 and 10 in the nine palace space, so that the sum of the three numbers in each horizontal, vertical and oblique row is equal to 18
• 3. Find the next number of the sequence 0.5 1 2 5 17 107
• 4. One number in the first bracket, two in the second bracket, three in the third bracket and one in the fourth bracket The cycle is divided into (1), (3, 5), (7, 9, 11), (13), (15, 17), (19, 21, 23), (25) Then the sum of the numbers in the 50th bracket is () A. 390B. 392C. 394D. 396
• 5. If the product of 100 rational numbers is positive, how many negative numbers are there at most? What is the sum of all possible negative numbers There are several numbers, the first number is A1, the second number is A2, the third number is A3, etc., and the nth number is an. If A1 = half, starting from the second number, each number is equal to the reciprocal of the difference between 1 and the number in front of it. (1) Try to calculate: A2 = (A3 = (), A4 = () (2) According to the above calculation results, we can guess: A1998 = (), a2000 = ()
• 6. A book, the first day read 20 pages, the second day read 14, two days read a total of 45 pages?
• 7. A freight car and a passenger car leave from Jiaji and meet each other in 4 hours. It takes 12 hours for the train to complete the whole journey, and how many hours for the passenger car?
• 8. The original speed of a car is 30 km / h, now it starts to accelerate evenly, increasing by 204 km / h; a car? A The original driving speed of a car is 30 km / h, and now it starts to accelerate evenly, increasing the speed by 204 km / h per hour; the original driving speed of a car is 90 km / h, and now it starts to decelerate evenly, decelerating by 10 km / h per hour. After how long, the speed of the cars is the same? What is the speed at this time?
• 9. The diameter of a car's outer tire is 9 decimeters, and the wheels roll 1000 cycles per minute. How long does this car advance per hour?
• 10. The distance between the two places is 360km, and they meet in two hours. The speed ratio is 5:4. How many meters are there in each line?
• 11. There were two granaries A and B. in the past, warehouse B stored 1 / 5 less grain than warehouse A. now, 1 / 4 of warehouse A's stock is put into warehouse B, and then 30 tons are transported from warehouse B. at this time, the two granaries stored grain together (don't use equations)
• 12. A, B and C make 940 parts at the same time. It takes 5 minutes for a part to be made by a, B and C, which is 25% more than that of B. the time for C to make a part is two fifths less than that of A. how many parts does a, B and C make?
• 13. The sum of a and B is - 2.6, B is - 7.5, how much is B bigger than a? The difference between a and B is - 4 / 3, B is - 1 / 6, what is a Please help me, thank you
• 14. The number a is 4 / 5 of the number B. how much less is the number a than the number B? How much more is the number a than the number B? の, write the formula,
• 15. The ratio of number a to number B is 2:5, and the ratio of number B to number C is 4:7 fast
• 16. In hope primary school, there were 325 boys and girls. In the new semester, there were 25 boys and 5 girls, and the total number of students increased by 16? Sixth grade, don't be too complicated
• 17. The number of male workers in a workshop is 25% more than that of female workers. Then: a. the number of female workers is 25% less than that of male workers. B. the number of male workers is 25% of that of female workers C. The number of female workers is 20% less than that of male workers
• 18. There are 480 male and female employees in a shopping mall, of which male employees account for 60% of the total number. Later, male employees transferred some people, and male employees account for 36% of the total number How many people have been transferred
• 19. A cement plant planned to produce a batch of cement in January. In fact, it completed one third of the plan in the first ten days, two fifths of the plan in the middle ten days, and another 26 tons in the last ten days. As a result, it exceeded one sixth of the plan. How many tons of cement are planned to be produced in January?
• 20. To process a batch of parts, it takes 12 hours for Party A to do it alone, 8 hours for Party B to do it alone, and how many parts are left after Party A and Party B do it together for one hour? We need to do it today