Ratios and Proportional Relationships 6.RP.A.3
3. Use ratio and rate reasoning to solve real-world and mathematical problems, e.g., by reasoning about tables of equivalent ratios, tape diagrams, double number line diagrams, or equations.
Diapers. An unfortunate and nonnegotiable element of the baby package.
This one-stop shop standard builds on students' knowledge of ratios and unit rates and applies them to real-life situations—and diapers, as we know, are very real. Need to know how many diapers that little monster goes through in a week? This standard has got you covered, with tons of visual aids to boot (tables of values, ordered pairs on the coordinate plane, diagrams, etc.).
It's a dirty job, but somebody's got to do it.