Make Math Moments Academy › Forums › MiniCourse Reflections › The Concept Holding Your Students Back › Lesson 62: Unpacking Ratios – Discussion › Reply To: Lesson 62: Unpacking Ratios – Discussion

John’s 2003 Saturn wagon goes an average of 16 miles per gallon in the city streets and 24 miles per gallon on the highway.
(This is a multiplicative comparison – the highway mileage is 1.5 times greater than the city mileage. The city mileage, in average, is twothirds of the highway mileage)
It costs John $30.00 to fill his car’s 12 gallon gas tank. Typically, he has to fill up every 240 miles. What is John’s cost per gallon of gas?
(This is a composed unit. I am going to use partitive division to reach the rate per gallon of gas: $30 divided by 12 is $2.50 per gallon. For each $1 John buys twofifths of a gallon of gas.)
One thing I noticed about the tables for these is that the multiplicative comparison table has values that can only be read vertically; but the table for gallons and cost can be read in both horizontal and vertical directions. (Not sure what this means though, or if it would usually or always be true!)