What is the value of gravitational intensity at the surface of Earth and at the Earth's centre?

Explanation

Gravitational intensity at a point distance `r` from
a point mass body of mass `M` is `I = (GM)/(r^(2))`.
For a point on the surface of Earth, `r = R`.
`I = (GM)/(R^(2)) = g = 9.8 m//s^(2)`.
For a point at the centre of Earth, `g = 0`, so gravitational intensity at the centre of Earth is zero.