The basic rule for this checksum is that each of the first nine digits is multiplied by its position (that is, the first digit times one, the second digit times two, and so on).
这个校验和的基本规则是前九位数的每一位乘上它的位置(即第一位数乘上1，第二位数乘上2，依次类推)。
2
Turns out the rule holds: he'd had nine years of intensive study.
10年定律是适用的：他此前进行过9年的集中强化学习。
3
What about Bobby Fischer, who became a chess grandmaster at 16? Turns out the rule holds: he'd had nine years of intensive study.