Upcoming SlideShare
×

# The Back of an Envelope (at Ignite NewsFoo)

2,755 views
2,595 views

Published on

Ignite presentation by Andrew Walkingshaw (@covert) of Timetric (http://timetric.com/, @timetric) at Ignite! NewsFoo

1 Like
Statistics
Notes
• Full Name
Comment goes here.

Are you sure you want to Yes No
• Be the first to comment

Views
Total views
2,755
On SlideShare
0
From Embeds
0
Number of Embeds
416
Actions
Shares
0
25
0
Likes
1
Embeds 0
No embeds

No notes for slide

### The Back of an Envelope (at Ignite NewsFoo)

1. Andrew Walkingshaw @covert, @timetric http://timetric.com/The back of an envelope.
2. Enrico Fermi (1901-1954)
3. Trinity Test: July 16, 1945
4. 10 One. 1 10 100Orders of magnitude
5. Three rules: 1. State your assumptions 2. Justify your guesses3. Be “dimensionally consistent”
6. Population of Chicago: ~5,000,000 Households: 5,000,000 / 2 people ≈ 2,500,000 Pianos: 5% of households ≈ 125,000 pianos Assume: each piano tuned once a year, taking ~2 hours: => ~250,000 piano-tuning hours=> 250,000/8 hours per tuning day ≈ 30,000 days 200 working days a year => around 150 tuners
7. And, actually:290 “musical instrument repairers and tuners” – (source: Bureau of Labour Statistics, 2009)
8. Sanity check.
9. How big is the US newspaper industry?value ≈ number of papers sold x revenue per paper npapers * \$/paper = \$total