Here's another possible interpretation for your mysterious problem:
If you multiply 2/5 by 1, you will surely end up with 2/5, right? And, 1 can be written in many different ways. For example, 3/3 is a name for 1. So, if we multiply 2/5 by 3/3, we'll get something that is equivalent to 2/5:
(2/5) * (3/3)
2*3
-----
5*3
or, 6/15, which is equivalent to 2/5
If you can be more specific about your question, we can provide an appropriate answer.