Look at the cards below.
Use the cards to answers these questions:
Do the same for litres of water per gram of protein.
Which other measures could you use to order the foods? Which do you think is the "best" food?
You can download a complete set of cards, and use them to play "Top Trumps".
You can find more information about the cards here.
This problem is based on the work done by Sarah Bridle and her colleagues at "Take a Bite out of Climate Change".
You can hear about Sarah Bridle's mathematical journey in this "The Life Scientific" podcast