A body weighs 200 N on the surface of the earth. How much will it weigh half way down to the centre of the earth ?

100 N

Acceleration due to gravity at a depth d from surface of earth

g′ = g(1 - \(\frac{d}{R}\)) -------(1)

Where g = acceleration due to gravity at earth's surface
Multiplying by mass 'm' on both sides of (1)

mg′ = mg(1 - \(\frac{d}{R}\))   (d= \(\frac{R}{2}\))

       = 200(1 - \(\frac{R}{2R}\)) = \(\frac{200}{2}\)

       = 100N