Sphere With A Cavity

answered by kaymant sir some time ago (long time) in reply to a sky didi's or tapan bhaiya's post

Ull have to use superposition principle

can u give me the link asish [1]

http://targetiit.com/iit-jee-forum/posts/easy-iit-07-4128.html

using the superposition principle as shown here,, u should be able to solve the question