Unit rate involves division.
Examples: a car travels 90 miles in 2 hours. The unit rate is 90/2=45 miles per hour.
10 ounces of candies cost $1.50. The unit rate (dollars per ounce) is 1.50/10=$0.15 or 15 cents per ounce.
A 490-page book takes a week to read. The unit rate of pages per day is 490/7=70 pages per day.
A car can travel 300 miles on a full tank of fuel. The tank holds 12 gallons of fuel. The unit rate (miles per gallon) is 300/12=25 miles per gallon.
The word “per” is equivalent to ÷ or “divided by”.