Solution: If the number of groups in this class is X, then there are 3x+ 10 people in this class.

According to the second method, you can get.

0 & lt(3x+ 10)-5(x- 1)& lt； = 1

Get 7

So x=7.

Therefore, the class size is 3 1, and it is planned to be divided into 7 groups.