Ratios, Rates, Proportions and Units on the Digital SAT: the Desmos Method
Every rate, ratio and unit conversion is the same straight line through the origin — graph it once and read any value you want off it.
Problem Solving & Data Analysis·65 practice problems in DesPrep
The Ratios, Rates, Proportions and Units lesson is part of DesPrep
It is one of the 17 full lessons inside the subscription — 6 sections that take ratios, rates, proportions and units from first principles to the fastest Desmos route, with a worked example on every one:
- A rate is a line through the origin
- Fractions: the right arrow key is the whole trick
- Units multiply. They never add
- Squares and cubes: once per direction
- Rates stacked on rates
- When a ratio does not give you counts
Then 65 practice problems on this skill alone, solved inside a live Desmos calculator with step feedback and an expert replay on every one.
More Problem Solving & Data Analysis guides
- Scatterplots and ModelsGraph a line of best fit and read predictions straight off it, instead of substituting by hand.
- PercentagesPercent change and growth, set up so Desmos does the arithmetic and the graph shows the trend.
- Distributions, Center and SpreadMeans, medians and ranges computed in the Desmos list bar rather than on paper.
- ProbabilityTurn counts into a probability, reduced correctly every time, and keep track of which total the question restricts you to.