A unit rate is a rate in which the second quantity is written as 1 unit.
For example, if you are driving and cover 60 miles in 2 hours, you would calculate the unit rate to find out how many miles you cover in 1 hour. To do this, you divide 60 miles by 2 hours, giving you 30 miles per hour. Here, the unit rate is 30 miles per hour, where the second quantity (hours) is written as 1.
Therefore, the correct definition of a unit rate is:
A unit rate is a rate in which the second quantity is written as 1 unit.
