One of my classes has been exploring rates and ratios. We started off the lesson sequence by using tiles and eventually moved towards rate tables. The class used simulations and the paint Desmos deck. The class progressed nicely through the different ratio/rate models and late last week we began our final task of the unit. This task was adapted from the Chicago Everyday Math resource and I thought it was a nice blend between current events and rates.
In 2021, Texas was hit with a record winter storm. The storm knocked out power supplies across the state causing a shortage of electricity. Electricity is measured in kilowatt-hours. Customers are charged according to how many kilowatt-hours they use. An average household uses just over 30 kilowatt-hours per day.
Before the storm hit, customers who had a variable rate were paying on average about 12 cents per kilowatt-hour. Because of the shortage caused by the storm, some customers had their variable rates go up as much as 9 dollars per kilowatt-hour.
How much would a typical household on a variable rate contract pay for electricity for five days without a storm?
How much would a typical household on a variable rate contract pay for electricity for five days at 9 dollars per kilowatt-hour?
Why might some customers claim their bills are not fair? Make a mathematical argument to justly your claim.
This was a challenge for students. Students read through the directions at least a couple times and still had questions. The questions dealt more with the significant difference between $9 per kilowatt hour compared to $0.12. They asked how that could be possible? Is that even legal? Why was it so cold in Texas? Is it because of climate change? I appreciated their curiosity and willingness to think about this as a fairness issue. This discussion lasted around 15-20 minutes. We then dove into creating a rate table.
Students first found out how many kilowatt hours a typical family uses in five days.