Hello...

You can score good marks by preparing the NCERT back questions but, I won't suggest to rely only on them because, sometimes CBSE asks conceptual and value based questions and for that you must study the topics thoroughly. As economics is a subject mixed with theory and calculative topics so, you must have proper practice for it and only back questions are not enough for it. Conclusively, I would say that if this subject isn't your strength then, you can rely only on the back question otherwise go for the full chapters.

Thanks!

All the best!

Not only back question but you need to go through all the chapters and each question if you want to score best , because ncert books are good for competition level entrance exam they will help you further in future so go through everything even basics of each topic given in your ncert book .