Fermi Estimation

Super-scientific guesses

But Really

Interview Questions!

Also great for technology

Also great for technology

provide the basis for a discussion

Also great for technology

provide estimates for a project

provide the basis for a discussion

Also great for technology

provide estimates for a project

estimate the feasibility of an opportunity

provide the basis for a discussion

Also great for technology

provide estimates for a project

estimate the feasibility of an opportunity

determine if an answer that you have obtained makes sense

provide the basis for a discussion

The Technique:

The Technique:

Identify the components of the answer

The Technique:

Divide the problem into small steps

Identify the components of the answer

The Technique:

Identify all the information you have

Divide the problem into small steps

Identify the components of the answer

The Technique:

Identify all the information you have

Determine what you have enough information for to factor into your problem

Divide the problem into small steps

Identify the components of the answer

The Technique:

Identify all the information you have

Determine what you have enough information for to factor into your problem

Divide the problem into small steps

Make an order-of-magnitude guess for what you don't have

Identify the components of the answer

The Technique:

Identify all the information you have

Determine what you have enough information for to factor into your problem

Divide the problem into small steps

Solve each step

Make an order-of-magnitude guess for what you don't have

Identify the components of the answer

The Technique:

Identify all the information you have

Determine what you have enough information for to factor into your problem

Divide the problem into small steps

Solve each step

Combine each step into an answer

Make an order-of-magnitude guess for what you don't have

Identify the components of the answer

The Technique:

Guessing

Rounding makes things easier to calculate- we only really care about orders of magnitude

The Technique:

Guessing

Rounding makes things easier to calculate- we only really care about orders of magnitude

Item    Exact Value    Suggested Value (for faster calculation)

    1 day    24 hours    25 hours

    1 mile    5280 feet    5000 feet

    1 yard    0.9144 meter    1 meter

    1 foot    30.48 cm    30 cm

    1 pound    453.6 g    500 g

    1 hour    3600 seconds    4000 seconds

Identify all the information you have

Identify all the information you have

How many kilometers are there in a light-year? 

Identify all the information you have

How many kilometers are there in a light-year? 

How long is a light-year?

Identify all the information you have

How many kilometers are there in a light-year? 

How long is a light-year?

c = 186,000 miles / second

Identify all the information you have

For the average American, how many times will their heart beat during their lifetime?

Identify all the information you have

For the average American, how many times will their heart beat during their lifetime?

What do we know?

What do we have to guess?

Divide and Conquer

How many heartbeats are there in a year for the entire world's population?

Divide and Conquer

How many heartbeats are there in a year for the entire world's population?

What smaller problems is this composed of?

Divide and Conquer

How many heartbeats are there in a year for the entire world's population?

What smaller problems is this composed of?

How fast does one person's heart beat?

Divide and Conquer

How many heartbeats are there in a year for the entire world's population?

What smaller problems is this composed of?

How fast does one person's heart beat?

How many heartbeats per year?

Divide and Conquer

How many heartbeats are there in a year for the entire world's population?

What smaller problems is this composed of?

How fast does one person's heart beat?

How many people are there?

How many heartbeats per year?

Divide and Conquer

How many heartbeats are there in a year for the entire world's population?

Earth's population * Heartbeats per year

Divide and Conquer

How many heartbeats are there in a year for the entire world's population?

Earth's population * Heartbeats per year

2,400,000,000 heartbeats per year in the US

Making Multiple Guesses

How many pounds of rice were consumed in the U.S. in the year 2015?

Making Multiple Guesses

How many pounds of rice were consumed in the U.S. in the year 2015?

How many people in the US?

Making Multiple Guesses

How many pounds of rice were consumed in the U.S. in the year 2015?

How many people in the US?

How much rice does a person eat?

Making Multiple Guesses

How many pounds of rice were consumed in the U.S. in the year 2015?

How many people in the US?

How much rice does a person eat?

5,200,000,000 lbs (Source: USDA)

Fermi Estimation

By LizTheDeveloper

Fermi Estimation

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