I recently got to know about an NCERT app by the name of NCERT solutions. The app is free to download and is launched by Eduwizards, the app lists down 7500+ questions and their answers.
There are all chapters in it with NCERT questions and free solutions. I strongly recommend all my friends to download this app. I did it myself and finding exam preparation extremely easy now. It is quiet easy and effective. I would say the best way to study for CBSE exams.