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How many trees are there in the world?
How many grains of sand are there on all the beaches in all the world?
Look for the answers online at tpt.aapt.org. 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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