please solve this.....

The acceleration due to gravity at the surface of Earth is

 g = GM /R²  .....................................................(i)

Let at height 'h' from the surface of earth, the acceleration due to gravity is 64% less than that on the surface of earth

so,   0.36 g = GM / ( R + h) ²...............................(ii)

From (i) and (ii)

g / 0.36 g  =  ( R + h) ² / R² 

1/ 0.6  = ( R + h)  / R

1 +  h/R = 1.67

h/R = 0.67

h = 0.67 R