Hehe, I am in the sixth grade. This question is actually not difficult. You can start with unfinished "1", and the total length is 1+ two-thirds = five-thirds. Then dividing one third by three fifths equals two fifths, which is 40%. You can also use the number of copies: two copies are repaired, three copies are not repaired, and the total length is 2+3=5, while 2÷5+ two fifths, that is, 40%, which is a bit verbose. . . . . . . Hope to adopt ~