Siddhant, it totally depends on the no.of hours that you can dedicate for NEET preparation. But ideally, if you look at the sylabus, it is only your 11th and 12th subjects. So even if you start reading your every day topics that have been taught in the class the same day, by the time you are ready for NEET, you will have revised the subjects atleast twice. And then if you can practise one mock test a week, that makes it as many as 100 mock tests approximately. That should be good enough. You can still afford to have "am lazy and cant read today" and "cheat days". So all in all you will be ready if you start preparing from your 11th. We at Careers360 also have come up with online preparatory courses which can help you prepare for NEET at your own pace. You can check that at:https://learn.careers360.com/knockout-neet-may/
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