Students should not be expected, or expecting, to get all the labels in the correct place on their first attempt! Encourage them to change the ordering of the "wrong" labels after pressing submit, and iterate this process until they arrive at the correct ordering.
Students can discuss the assumptions made in calculating the carbon savings and whether they think that these are reasonable assumptions to make.
This problem is one of a collection designed to develop students' carbon numeracy; we hope it will encourage students to think about the issues surrounding climate change. You can find the complete collection here.
This problem also featured in an NRICH Secondary webinar in November 2021.
Below is the collection of cards used in the problem.
The numbers show how many kg of CO2e you might save per year by making the changes. They all make the assumption that you are in the UK.
Turn the TV off when you aren't watching it
(Assuming it is off for 2 more hours each day) 8
Avoid over-filling the kettle
(Boil 1 mug less each time, 5 times a day) 10
Run the dishwasher only when it is full
(Assuming this means you run it one less time each week) 13
Turn your computer off when not in use
(Assuming it spends 20 hours a day in standby mode) 16
Let the sun dry your washing
(Instead of tumble drying 2 times a week) 27
Repairing, instead of replacing, a vacuum cleaner
(Based on research by The Restart Project) 36
Install a low-flow shower head
(Assuming a 7 minute shower a day, heated by gas boiler) 45
Cutting out nearly all food waste
(Based on research by Wrap) 49
Repairing, instead of replacing, a smartphone
(Based on research by The Restart Project) 51
Share your car trip to school with a neighbour
(Instead of a 1.3 km trip 10 times a week) 95
Return trip to Dublin by train/ferry instead of by air
(The plane trip is 470km. By train and ferry it is 590km.) 108
Repairing, instead of replacing, a medium sized laptop
(Based on research by The Restart Project) 265
Switching to a renewable-based electricity supplier
(Based on an estimate from Good Energy) 745
Paying for something by debit card instead of Bitcoin
(Based on an estimate from Diginomics) 853
Return trip to Paris by Eurostar instead of New York by air
(Paris is 400km away, New York is 5600km) 1009
Switching from a meat-heavy diet to a vegan diet
(Based on research by Professor Peter Scarborough) 1500
Take a holiday in Barcelona instead of Melbourne
(Melbourne is 16,904km away, Barcelona is 1138km) 4650