A rate is a special ratio in which the two terms are in different units. For example, if a 12-ounce can of corn costs 69¢, the rate is 69¢ for 12 ounces. ... When rates are expressed as a quantity of 1, such as 2 feet per second or 5 miles per hour, they are called unit rates.
Some examples of rate include cost rates, (for example potatoes cost R16,95 per kg or 16,95 R/kg) and speed (for example, a car travels at 60 km/h). When we calculate rate, we divide by the second value, so we are finding the amount per one unit.
*r^2. Hope this helped!