What Altitude Above Earth Gives a Gravitational Acceleration of 3.53 m/s²?

[Punchlinegirl]

At what altitude above Earth's surface would the gravitational acceleration be 3.53 m/s^2?

I used the equation
a= GM/r^2
G=6.67 x 10^-11 and M= 5.98 x 10^24
Solving for r gives 1.06 x 10^7 m which isn't right... can someone tell me what I'm doing wrong?

 

[Galileo]

Reread the question. You need the altitude above the Earth's surface, not the distance from the center of gravity of the earth.

 

[Punchlinegirl]

How would I find that since all I know is the acceleration, mass and radius of the Earth?

 

[whozum]

You know r = 1.06 x 10^7 m, the problem isn't asking for 'r'.

The problem is asking how far from Earth's surface. You know 'r' of earth, how high above the Earth is r = 1.06 x 10^7m?