How would one plug the gravitational constant into an equation? To be honest, I'm having a hard time with the idea of the gravitational constant in general, but I need to solve an equation for the circular velocity of a galaxy. I know I need to multiply the gravitational constant by the mass (1.313x10^40 kg) and divide that by the radius (5.676x10^17 m) and the square root of that is somehow my answer, but I'm not sure how it all works. Any help is appreciated!
If the mass of the Galaxy is all at the center the angular velocity at distance R is given by
ω = sqr(M•G/R^3),
where M = central mass kg,
G = gravitational constant 6.67 x 10-11 Nm2kg-2,
R = distance from central mass m