Using dimensional analyisis to verify formulae

BogMonkey

Heres a question I never figured out.

"Using dimensional analysis, determine which formula (a) or (b) is correct for the description of the force due to gravity between a body of mass m (kg) and another of mass M (kg) separated by a distance of r (m). The gravitational constant G has units (m^3s^-2kg^-1)
(a) FG = G m M / r^2 (b) FG = G m M ./ r"

I've been looking up dimensional analysis but can't find any information relating to validating formulae.

Doc Al

For an equation to be physically meaningful, the units on each side must match. Check the units in these two and see what you find.