In many ways, CBSE sample paper for class 10 and 12th board exam helps student:
1. It puts a lot of confidence when you complete it within the limited time frame.
2. By solving it you can analyze your weaker section of chapters which you have to focus more and learn it.
3. Also, it helps you in time management, in overcoming the mistakes you have done earlier.
However, The sample paper not exactly matches with the Board question paper but there are several instances we see questions in sample paper matches with the board question paper. There are several repeated questions also. But don't ever rely on that. Put your efforts to score better by practising it more and more.
You can download sample papers and its solution from
Class 10 sample paper
Class 12 sample Paper