FERMIE PROBLEMS

1
FERMIE PROBLEMS
FIRMI PROBLEMS

• Missing Information, Assumptions, Estimation

FUN WITH ESTIMATION
2
Introduction

• How Many Trees are there in Ontario?

3
Introduction

• How Many Trees are there in Ontario?
• How long would it take you to count by ones to
  one billion?

4
Introduction

• How Many Trees are there in Ontario?
• How long would it take you to count by ones to
  one billion?
• These types of problems are called Fermi Problems.

5
Continued

• To solve Fermi problems, you need to find missing
  information, make assumptions, and use
  estimation. Other problem solving strategies
  may also be useful.

6
Continued

• To solve Fermi problems, you need to find missing
  information, make assumptions, and use
  estimation. Other problem solving strategies
  may also be useful.
• Remember that your answer to a Fermi problem will
  be approximate. Answers may vary from person to
  person.

7
Examples

• How many times does a dog wag its tail in its
  lifetime.

8
Examples

• How many times does a dog wag its tail in its
  lifetime.
• What do we need to do?
• Where do we start?

9
Examples

• How many times does a dog wag its tail in its
  lifetime.
• What do we need to do?
• Where do we start?
• Assumptions
• Dog wags tail once per second on average
• Dog lives for 10 human years

10
Where do we Start??

• What do we know?
• Dog wags tail a lot
• Dog lives for 10-12 years

11
Where do we Start??

• What do we know?
• Dog wags tail a lot
• Dog lives for 10-12 years
• Assumptions
• - Dog wags tail once / second
• - Dog lives for 10 years.

12
The Math

• 1 wag 1 second 60 seconds / minute
• 60 wags / minute 60 minutes / hour
• Wags / hour 60wags x 60 mins 3600 wags /
  hour.
• 3600 wags/ hour 24 hours / day
• Wags / Day 3600 x 24 hours 86 400
  wags / day
• 86400 wags / day 365 days / year
• Wags / Year 86 400 x 365 days 31 536 000
  wags / year
• 31536000 wags / year 10 years of
  life
• Wags / Life 31 536 000 x 10 315 360 000
• Wags / Life 3.153 6 x 108
• A dog wags its tail approximately 3.153 6 x108
  in its lifetime.

13
Tricks

• Break the question down.

14
Tricks

• Break the question down.
• Figure out what you know.

15
Tricks

• Break the question down.
• Figure out what you know.
• Make assumptions.

16
Tricks

• Break the question down.
• Figure out what you know.
• Make assumptions.
• Make Estimates.

17
Tricks

• Break the question down.
• Figure out what you know.
• Make assumptions.
• Make Estimates.
• Try different methods.

18
Tricks

• Break the question down.
• Figure out what you know.
• Make assumptions.
• Make Estimates.
• Try different methods.
• Answers will vary from person to person.