How much water can you boil with the energy stored in a cell phone battery? (Thanks to Donna Andrews for inspiring the question in her new book Terns of Endearment.)

How much does the electrical energy for a cell phone cost each year?

Look for the answers online at under “Browse,” at the very end of the current issue.

Question suggestions are always welcome!

For more Fermi questions and answers, see Guesstimation 2.0: Solving Today’s Problems on the Back of a Napkin, by Lawrence Weinstein (Princeton University Press, 2012).

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