Fermi Problems - How Many Soi Dogs are there in Phuket?

A Fermi problem is an estimation problem named after the Enrico Fermi, a twentieth-century, Nobel Prize winning Physicist using very little information.

MYP5 have been working on estimations using sound reasoning and then calculating the absolute percentage error from the excellent site Estimation 180. Other classes have used this site too and it's a wonderful way for anyone (grown-ups too) to develop their number sense. 

It is now time for MYP5 to go a step further and ask a question where the answer is not readily available. Good reasoning will be important here. 

Below this video from ed.ted.com are some famous examples.

 

The circumference of the Earth – using time zones

1.     How many time zones do you pass through when you fly from New York to Los Angeles? 3

2.     How many miles is it, about, over that same distance? about 3000.

3.     How many miles per time zone, on average? about 1000

4.     How many time zones must there be around the world? 24 because there are 24 hours in a day

5.     How many miles around the world? 24 time zones x 1000 miles per time zone = 24000 miles

About 24000 miles around the world.

Fermi's Piano Tuner Problem 

1. At that time Chicago had a population of about 3 million people.
2. Reasonable assumption: average family size is four. Therefore the number of families in Chicago is around 750,000.
3. Reasonable assumption: one in five families owns a piano. Therefore the number of pianos in Chicago will be around 150,000.
4. Reasonable assumption: the average piano tuner serviced four pianos every day for five working day and had two weeks holiday.

We can calculate that in one year a tuner would service 1,000 pianos. 

There is an estimated 150 piano tuners in Chicago.

Example of Fermi Questions:
How many nails are in the Pirate Ship? 
What is the volume of air that I breathe in one day?
How many people in the world are taking photos with their phones in any given minute?
How many soi dogs are on the island of Phuket?