Arrange the natural numbers as follows: 1. The last number in line 30 is () 2. There are () numbers in the first 40 lines. 3. The first number in line 28 is () one 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16

Arrange the natural numbers as follows: 1. The last number in line 30 is () 2. There are () numbers in the first 40 lines. 3. The first number in line 28 is () one 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16

The numbers of 1. Are: 1, 3, 5, 7, 9
What is the number of the thirtieth row? It is equivalent to the number of the thirtieth of the above arithmetic sequence
(30-1) * 2 + 1 = 59, line 30 is 59,
The last number in the first line is 1,
The last number in the second line is 1 + 3 = 4
The last number in the third line is 1 + 3 + 5 = 9,
...
The last number in line 30 is 1 + 3 + 5 + 7 +... + 59 (the sum of 30 numbers) = 900,
2. The calculation method of the total number of the first 40 rows is similar to that of 1, which is equivalent to the sum of the first 40 items in the sequence, equal to 1600
3. It is equivalent to the sum of the first 27 items of the sequence, plus 1