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Feel free to discuss the answers by adding annotations. (Group annotations are currently unavailable, supposedly to return in a much better invocation later.)

In a Fermi question, the goal is to get the answer to an order of magnitude (power of ten) through reasonable assumptions about the situation, not necessarily relying upon absolute knowledge for an "exact" answer.


1. Ignoring oceans and such, how long would it take to walk entirely around the world?

2. How much water per year flows past New Orleans?

3. How many dumptruck loads would it take to move Mt. Fuji? How long would it take?

4. In the song "In the year 2525" by Zager & Evans, it is sung that "man cried a billion tears." How much water is that? Would it cover the entirety of, say, Central Park? How deeply?

5. What is the linear velocity of the earth around the sun?

6. What is the speed of light (in a vacuum) given in:

  1. furlongs per fortnight?
  2. feet per year?
  3. angstroms per millenia?

7. How many drops of water are in the Atlantic Ocean?

8. How many ping pong balls would it take to fill the Washington Monument?

9. How much human blood is there in the world?

10. How many books are in a bookstore?

11. How many bricks are in a wall?

12. How big is a one-millionth scale map of the US?

13. How many atoms are in a cell?

14. How many sugar cubes are in a box?

15. How many servings of rice are in a fifty-pound bag?

16. How many people do you know? How many people do they know?

17. How much does it cost to run an ad in the National Enquirer? ($200) How many people will read it?

18. What is the GNP per capita?

19. How many lightbulbs burn out in one minute?

20. How many hours do you have to work to pay for a car?

21. How long would it take you to build a car? A loaf of bread? A sweater?

22. How long does it take to paint a house? How much paint would you use? How long would it take to dry?

23. How long would it take to make dinner for twelve people? Where would you put it while you were waiting to serve it?

24. How high can a flea jump? A cat? A human? An elephant? What is the optimum size of a jumping animal? (A horse?) (A grasshopper?)

25. Note the scale of a millimeter vs. a meter, now imagine something 1/1000 mm, now imagine something 1000 m, imagine them both at the same time; you are now contemplating one billion.

26. How high are a million kids standing on each other's shoulders?

27. How large a bowl would you need to hold a million goldfish? ("large enough to hold a whale!")

28. How long a row of pages would be needed to show a million stars?

29. How long would it take to count to a million?

30. Imagine you had a rope stretched tight round the earth and you spliced a yard more rope into it. Could you now get a coin under it?

31. How many piano tuners are there in New York City?

32. How many cells are in the human body?

33. How many grains of sand on Goleta beach?

Recommended Reading:

"How Much is a Million" by David Schwartz
"Metamagical Themas" by Douglas Hofstatder
"Innumeracy" by John Allen Paulos
"Used Math" by Clifford E. Schwartz
"Aha" and "Aha - Gotcha!" by Martin Gardner 

Netscape HTML Checked! November 16, 1993 - Robert Lentz (

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