How to solve this ratio/proportionality question?

1. Nov 17, 2014

Tangeton

The Moon's gravitational pull on the Earth causes the ocean tides. Show that the gravitational pull of the Moon on the Earth's oceans is approximately 3 millionths of the gravitational pull of the Earth on its oceans. Assume that the distance from the Earth to the Moon is 380,000 km.
Other given/worked out previously: mass of moon = 7.35 x10^22kg, surface gravitational field strength of the moon: 1.62Nkg^-1, radius of the moon = 1740km (3sf)

g at the earth's surface is 9.8.
g at moon's surface I worked out using the formula g = GM/r^2,g * mass of moon/ distance from moon to earth sqred = 3.40x10^-5 (3sf)

My big problem is the ratios. How do I show that its 3/1000000 of the grav. pull of the Earth? I know that grav pull of the earth on oceans will be 9.8 and the moon on the ocean will be 3.40x10^-5, but I just simply do not know how to do physics ratio questions whatsoever. I am terrible at them... How do I approach ratio/ proportionality question such as this one? What is the process?

2. Nov 17, 2014

Vagn

You're nearly there, what do you get if you divide the moon's pull on the ocean, by the Earth's?

3. Nov 17, 2014

Tangeton

Okay that was too easy. Thanks.