В чем разница между rate и ratio ?Пожалуйста, приведите примеры.

A rate describes the relationship between an dependent (not directly controllable) quantity and one or more independent quantities. It is common for the variable quantity to be a measure of time (as in meters per second or revolutions per minute), but not required. For instance, one might measure the rate of food costs in dollars per man-meal. If you increase the number of meals or the number of people at each meal, the food cost will rise proportionately, but we cannot control the food cost itself—it depends on those other quantities. You can think of the rate as the slope/gradient of the graph plotting those quantities against one another (with the dependent variable on the vertical axis as is traditional). Basically, if you use the word “per” to describe the units of the combined quantity, it's a rate.

A ratio is used to show the relationships between quantities any of which can be varied independently. For instance, I could say that 12 lbs. of malt, 2 oz. hops, 1 pkg. yeast and 6 gal. water make 1 keg of lager, for a ratio of 12:2:1:6:1. If I want to vary any of these quantities—use more hops, use less major, make a smaller batch, etc. I can do so as long as I vary the other quantities to keep them all in this same ratio. The colons used to write a ratio are usually pronounced “to”.