How much below the earth's surface the acceleration due to gravity reduces to 64% of its value on the surface of earth ?

How much below the earth's surface the acceleration due to gravity red

1.	How much below the earth's surface the acceleration due to gravity reduces to 64% of its value on the surface of earth ?
Answer» Solution :`g. = (64)/(100)g` `(g.)/(g) = (R^(2))/((R+h)^(2))` `(64)/(100) = (R^(2))/((R+h)^(2))` `RARR (8)/(10) = (R )/(R + d)` `8R + 8d = 10R` `8d = 2R rArr d = (1)/(4)R` `d = (1)/(4)R = (1)/(4) XX 6,400 = 1,600 km`