Math problem in the fourth grade of primary school: a nine-digit number, the sum of the numbers on each digit is 15, in which the number on the ten thousand digits is twice that on the one hundred million digits. What is the maximum quantity? Maximum 430080000, minimum 100020039. If you think about it this way, these nine numbers can only be one of the ten numbers of 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, and the number of tens of thousands is twice that of hundreds of millions. Find the middle two correlations: 1 and 2,2 and 4,4 and 8. If you want this nine-digit number to be the most important, it should be above 100 million digits, so 100 million digits is 4 and 10 thousand digits is 8. These two numbers add up to 12, and there is a 3, which is the largest in a million. The minimum number of 65438+ 100000 digits is 2, which adds up to 3 15-3 = 12, and 12. Just now I said that these nine numbers can only be 0, 1, 2, 3, 4, 5, 6, 7, 8. The smallest is 3 and 9, but the smallest is to put 3 in the tenth place. I hope you understand.