which should I choose?

qwrersaa

某人有bookcase, arrange 10 books per shelf and no books left. If he acquired 10 additional books, and arrange 12 books per shelf, no books left. Ask how many books he has before acquiring the addition 10 books
1) before acquiring, his books less than 96
2) before acquiring, his books more than 24
which should I choose?
Thank you very much

sammen

条件1可以，条件2不可以。设原来有书x本，从题目得x/10和(x+10)/12都是整数。安条件1可以得出x=50;而条件2可以得出很多结果，x=50,110,170等等很多。

qwrersaa

厉害，感谢了！！