Ratio is a fraction of two same units
(8 cups milk) / (3 cups sugar)      (cups is the unit here)
   8 cups milk to 3 cups sugar      (say to)
   8 cups milk : 3 cups sugar      :
You worked 40 hours to my 35 hours: 40 hours : 35 hours      Can be simplified to 8:7
Rent here: $900. Rent there: $800. Ratio of rent there to here: $800:$900

Rate is a fraction of two different units
200 miles per : to 5 gallons      per, to, :
   (200 miles)/(5 gallons)
Or, could be flipped: 5 gallons per 200 miles = (5 gallons)/(200 miles)
$1000 per 20 hours work
2 cups milk : 10 oz. butter

Unit rate: one in the denominator. Do the division. Average per 1 denominator unit.
(40 miles)/(1 gallon)= 40 MPG
200 miles in 4 hours = (200 miles)/(4 hours) = (50 miles)/(1 hour) = 50 MPH (average speed)
4 hours : 200 miles = (4 hours)/(200 miles) = (0.02 hour)/(1 mile) = (1.2 min)/mile
113 yen to one dollar      ¥113 per $
100 Calories / 1 medium apple      103Cal per apple
330 dollars for 300 euros = $1.10:€.      300€/$330=.9090€/$