A free program for Android, by Sana Edutech.
This app is the best for learning and understanding what is required in the exams for IIT, JEE, GATE, BITSAT, ENAT, VITEE, PACET, ATIT, ISAT, WAT, MERI, AMIE, JEE, ECET, VIT, KIITEE, SAAT, UPTU, RPET, COMEDK, UGET, CEE, OJEE, and other Engineering Exams.
The app contains over 100 questions that will help you in preparing for the exams. It is divided into different topics and subtopic areas. Each subtopic area contains a number of questions. You can mark the ones you have already solved and the ones that you have not.
You can also view the solutions to the questions. The solutions are written by experts in each field.