The acceleration due to gravity at a height 1 km above the earth is the same as at a depth d below the surface of earth. Then
d = 1 km
d=32 km
d = 2 km
d=12 km
The acceleration due to gravity at a height h is given as
gh=g1-2hRe
where Re is radius of earth.
The acceleration due to gravity at a depth d is given as
gd=g1-dRe
Given, gh=gd
∴g1-2hRe=g1-dRe
∴ d=2h=2×1=2 km (∵h=1 km)