a body weighs 300 N on the earth's surface. what is its weight at a depth of 1/3rd of radius of earth?

F=GmM/R²=mg

at surface F=300N=mg

m=300/9.8=30.61kg

gravity g' at depth d is  given by:

g'=g(1-d/R) 

here d=R/3

g'=2g/3=6.533m/s²

force at depth R/3

mg'=30.61×6.533=199.9N