Gravitational force

[Jt00]

The gravitational force between two masses is 36N. What is the gravitational force if the distance between them is tripled?
a. 4.0N
b. 9.0N
c. 18N
d. 27N


Formula for gravitational force: (Gm₁m₂)/r
G=6.67*10^-11
r: distance between two objects
m₁ and m₂: masses of two objects

My work: (m representing the products of mass 1 and mass 2) Gm/r = 36/1 Gm/3r = 36/3 Gm/3r = 12
But 12N isn't an answer... where did I go wrong?

 

[Someone2841]

Looks like you just have your formula wrong, it's \(\displaystyle r^2\).

\(\displaystyle G\frac{m_1m_2}{r^2}\)

 

[Jt00]

ok, thanks.