Toppr.com is the one of the best study qpps available at play store at present. I used it as a student many times .And it helps me a lot in achieving my target. The best thing about the app is that it gives the quick response and the faculty of this app which is working on it , is also cleared competition exam like iit jee , bitsat , jee mains , neet , kvpy and Olympiad etc . You can find this app on play store by searching topper . And it is very very useful for the students who are preparing for iit. thanks.