Sasha practices oral arithmetic. She sums from 1 according to the order of natural numbers. When he calculates a certain number, the sum is 1000, but she repeatedly calculates one of the numbers Using arithmetic sequence to calculate formula

Sasha practices oral arithmetic. She sums from 1 according to the order of natural numbers. When he calculates a certain number, the sum is 1000, but she repeatedly calculates one of the numbers Using arithmetic sequence to calculate formula

It's 1 + 2 + 3 + +X is just a little smaller than 1000
Then the maximum number x is about the square root of 2000
X = 44
1+2+3+…… +44 = (1+44)*44 / 2 = 990
The repeated number is 1000 - 990 = 10

For any natural number, first sum all the numbers, then multiply the sum by 3 and add 1. After repeated many times, the result is a fixed number r,

shenmeyisi?

Kimu began to sum from 1 according to the order of natural numbers. When she calculated a certain number, the sum was 888. But she repeated one of the numbers and asked which number was repeated?

1+2+.+40=820
888-820=68
The answer is 68