Cengage.co.in is indeed a great helper in making future of India. They provide IIT guides in each PCMB so that the students can tackle competitive exams like JEE, NEET, AIMS etc. Their series of books in those subjects have thousands of different kind of questions which may appear in competitive exams along with detailed solution. Also there mobile application gives the opportunity to take mock tests so that the students can manage time in main exams.
I tried their application which is too god and it really helps in cracking IIT.