Proportionality of gravitational fields

[Nikola]

Homework Statement

Scientist want to put a satellite into an orbit where the gravitational field of Earth is half its value at Earth's surface. The altitude of this orbit above the Earth's surface will be
A.3R B. √2R-R C. 4R D.√2R

Homework Equations

Fg∝1/r^2

The Attempt at a Solution

I know it is D. but i couldn't figure out how.

 

[tnich]

Homework Statement

Scientist want to put a satellite into an orbit where the gravitational field of Earth is half its value at Earth's surface. The altitude of this orbit above the Earth's surface will be
A.3R B. √2R-R C. 4R D.√2R

Homework Equations

Fg∝1/r^2

The Attempt at a Solution

I know it is D. but i couldn't figure out how.

Show us what you have tried. Maybe we can help you figure it out.

 

[Nikola]

i tried using the equation

 

[DanielA]

i tried using the equation

Here's how to use Latex to type formulas here https://www.physicsforums.com/threads/physics-forums-faq-and-howto.617567/#post-3977517
Please show us how you used the equation; what numbers you plugged in, and how you solved it. We can't really help unless you show us your attempts, even if they're basic.