1. The problem statement, all variables and given/known data The value of acceleration due to gravity at a point P inside the earth and at another point Q outside the earth is g/2 (g being acceleration due to gravity at the surface of earth). Maximum possible distance in terms of radius of earth R between P and Q is Ans: R/2 ( 2*root2 + 1 ) 2. Relevant equations Acceleration due to gravity at a depth d under the earth = g(1-(d/R)) Acceleration due to gravity at a height h above the earth = g(1-(2h/R)) g-acc. due to gravity at surface R- radius of earth 3. The attempt at a solution g(1-(d/R))=g(1-(2h/R)) d=2h g/2 = g(1-(2h/R)) g/2 = g(1-(d/R)) d=R/2 h=d/2=R/4 So, d+h= 3R/4 In all these steps, not once did I think about the maximum possible distance. And my answer is also wrong.