Back of the Napkin Math | In Depth

Now You Know

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    On today's episode of "In Depth" Zac & Jesse ask the question: Is back of the napkin math more important than Calculus? Watch and find out!
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    Publicat pe Acum 24 Zile



      This would is genius and would be disruptive to the rote banal school math drills, because it would stimulate imagination and actual creative thought. The current antithesis to school curriculum. I asked my son's math teacher why Soo much math homework compared to others classes, which was at least 2x. She said it is for "logical thinking". Hmmm. Sounds illogical to me.

    2. Totial

      I dont think the government likes ppl doing math... and i bet thats why schools are what they are. Good job BTW

    3. Just The Facts Please

      If you want some good 'history' on back of the napkin math, "Rocketship Galileo" by Robert H. Heinlein is a great book for use both as a great example of how to use it, but a little entertainment as well. It may be little dated now since it's primary audience was aimed at the Boy Scouts in the 1950's, but still, a very creditable example that many used. Not to mention most of his juvenile fiction. And if you want to see a slightly chilling example of Elon Musk represented by someone who could've never met him, read his "The Man Who Sold The Moon". Delos D. Harriman had nothing on what Elon can do. (And yes, you CAN Google Delos D Harriman and get back a very good Wikipedia article.) Back of the napkin math has both created and solved more problems than anyone could ever imagine. It was probably back of the napkin math that led Ford to say "Eh, it'll be cheaper to pay off the lawsuits and buy back the cars than it will be to make the changes. Let's do it that way." when the Ford Pinto gas tank fiasco was revealed back in the early 1980's. Oh, well. The bad with the good, right? Besides... for real math, all you need is a Post-It

    4. Richard DeVenezia

      6:16 2020 Word of the Year "Tiblet"

    5. walchemy

      I took a lot of math in college but don’t utilize it in my adult life, therefore, I’m losing my math muscle. I love what you guys are promoting - daily critical thinking! I will have to start using my brain again!

    6. Jack Emanuel

      I like meth, oh wait did yo0u say meth or math.?

    7. john mightymole

      I just did so e back of the napkin maths and calculated using the formula C - W = t where C = content, W=waffle t=time, this could have been much shorter. Roughly six hours shorter.

    8. Zhu Bajie

      You've discovered my favorite hobby. I use a spreadsheet like Elon but it's the same as a fancy napkin and more flexible (you can try several scenarios quickly). Sometimes I'm surprised by the answer such as how much more expensive a flight on an airplane would be if you used liquid hydrogen because the seats that would be taken up by the increase in the volume of the fuel (liquid hydrogen is very energy-dense per unit mass but not per unit volume).

    9. Gary Jonassen

      Educated guessing

    10. Palladin

      Hmm, like 4 years ago (maybe around the last Presidential Election), one of the well-know "thinkers" made a comment about how a significant portion of the US CO2 emission came from SemiTrucks. Unlike cars which "most" of the time only do 1 or 2 commutes (excluding taxis), a truck may be transporting cargo 8+ hours a day. He pointed out that if the US was to add more incentives to replace older trucks with fuel-efficient ones it would have a much more significant impact on CO2 (than car incentives (MAYBE this was around the time of "cash for clunkers"). Now that the Tesla Semi is coming out, maybe the government can start adding incentives in that area. It is already a business expense, so the cost can be deducted, but why not go beyond that. For example, if you are replacing a vehicle, the government can issue the purchaser a Carbon Credit based on what has been removed by retiring the old truck. (I think this would have very little out of pocket for the government). Or providing some other incentives.

    11. Roy Wessbecher

      It's called informed intuition.

    12. David Stein

      Jesse and Zac, you mentioned solving Global Warming. Multipronged approach: implement Holistic Management on 50% of world's grazing lands, promulgate Permaculture designs, turn Permaculture designers loose on reforestation efforts globally. Implement GreenWave techniques in continental shelf projects world-wide. Farm kelp in many coastal ecosystems for ethanol, biogas, energy, and sustainable fertilizer production. The oceanic techniques above will also lower oceanic surface temperatures with many positive effects. Read for additional details.

    13. k34561

      What irks me about this presentation is the notion that "Back of the Napkin Math" is new. I have been doing it for 40 years. The Apollo engineers used it get to the moon. In the natural sciences, back-of-the-envelope calculation is often associated with physicist Enrico Fermi,[2] who was well known for emphasizing ways that complex scientific equations could be approximated within an order of magnitude using simple calculations. The notion "Back of the Napkin Math" is new is wrong. Every top scientist/engineer has been using it to some extent.

    14. k34561

      What irks me about this presentation is the notion that "Back of the Napkin Math" is new. I have been doing it for 40 years. The Apollo engineers used it get to the moon. In the natural sciences, back-of-the-envelope calculation is often associated with physicist Enrico Fermi,[2] who was well known for emphasizing ways that complex scientific equations could be approximated within an order of magnitude using simple calculations. The notion "Back of the Napkin Math" is new is wrong. Every top scientist/engineer has been using it to some extent.

    15. frog42

      I actually do this stuff every week and for planning. I've gone from being in massive debt to paying off one credit card and I'll be paying the next one off. I've gone from no credit, bad credit, to great credit. Back of the napkin math is really powerful

    16. Moritz Sanne

      As a scientist, I would like to challange you and say: every big study and big project begins with a napkin :)

    17. Jeremey Wise

      So I have been watching various sessions for a while. Can we get someone to do real world session on what a tesla car would take in foot print and cost of PV to charge and maintain one Tesla Model3. AKA. We go "all electric" what would the footprint in PV need to just sustain one Model 3. Assume you can store with Powerwalls... but do "back of math" of what electricity it takes to drive 60 miles a day for typical commuter. What power would that consume. I have calculated my house as that I can get numbers based on my current electric bill (20kw and ROI is not working out yet... getting close though). But if I add EV car into investment what more in panels and poweralls would it take. Another question I had is... is Tesla's cars able to be used today as a 'power wall' AKA... one power wall holds house for up to 2 dark days... drive car to super charger.. charge up.. bring my power home to hold me over for the next x days till I get sunny day.

    18. Thisisanerror

      I don't think "back of the napkin math" was mentioned enough in this video

    19. D D D

      Do we have the production to facilitate that rate of expansion? Because so many companies are all requesting these wind turbines and solar, would there be enough to do it in a year for every company?

    20. jdear97

      I disagree on a number of fronts. They would need shareholder approval to to cut the dividend, I bet it would be a close thing and their share price would take a hit. 10 Billion dollars is a lot of money for Microsoft, they can afford it and I am glad to see them make the commitment. Being Carbon Neutral for all of the carbon ever produced by the company is a pretty admirable goal and you will have a difficult time proving that it hurts or helps the company bottom line. Finally, if they spend too much of the company money on projects that are not considered in the interest of the company, the board can be voted out and you could end up with a much less environmentally aware board of directors. You should call them out on the project if they do not stay on track; but don't be dismissive if they actually do achieve their goals. They are admirable goals and worthy objectives.

    21. stephen s

      I hate wind turbines for so many reasons

      1. Tag Makers Pet Tags

        I love wind turbines for one reason.

    22. Carpenter

      No need to overexplain. I'd ask your hero's choice and that he would say Calculus is more important for real world engineering.

    23. TexSweden

      As someone who actually works at the company you bashed - just buying something to OFFSET your CO2 production is easy. What Satya and Microsoft want to do is to change the entire value chain to be Carbon NEGATIVE. That includes changing or altering all the subcontractors, making sure the restaurant where an employee eats lunch is carbon negative, the transportation used, everything! Just planting a tree to Offset your CO2 production is not the point, that's EASY. What we're doing is showing that we can change our entire value chain and show that the entire company and all its subcontractors can change for the better! To do that for a value chain that spans 190 countries and millions of people, not to mention the billions of customers, in just ten years is a pretty bold goal in my eyes.

    24. George Hawley

      First principle-It’s easier to do math on paper placemats than on napkins.🤓

    25. john stubbe

      critical thinking and simple math ,the worlds building blocks

    26. john stubbe

      critical thinking and simple math ,the worlds building blocks

    27. WZLS Gamin

      amazing episode! love it

    28. Getaw Belku

      Yes we can find amazing things but how and who will acknowledge that is yours or someone’s invention once you put on the RO-sels and also the incentives.

    29. Robert Martens

      It seemed like a good idea at the time. But come on man. 3 minutes later, you are like, what should we talk about now?

    30. Ev Jedi

      🧻 that is one big ass napkin. I bet you could sell that napkin to Ford or GM at this point for a good dollar. LOL

    31. Robert Martens

      You jumped the shark man

    32. Robert Martens

      So odd you guys

    33. ANTY SPI

      Zac, Jesse, you have gone completely off the rails in this show, I´m afraid. A "Back of the Napkin" calculation is simply a rough calculation to check the validity of a very rough concept. That´s it. It is not the saving grace for science, economy or politics. You can start with a very rough calculation, but as soon as you flesh your concept out, you have to take more and more details into account. My experience is the opposite: Many people (especially managers) do the "Back of the Napkin" calculations and then try to do the whole project based on these, even though more and more details are learned and discovered that were not part of the first rough calculations, which can invalidate the whole thing. Elon did not make a "Back of the Napkin" calculation when he founded Spacex. When the negotiations with the Russians failed, he had already worked out a whole Excel table full of required parts and their pricings. In other words, Elon had already done a heck of a lot of research before even considering to found a rocket company. And guess what? Even then he was wrong and hat to spend more than twice the amount of money he had anticipated in order to get a rocket into orbit. The problem in politics is not that politicians can´t do short calculations and arn´t able to think logically (there are exceptions of course). The main problem is that most politicians have their own personal agenda, that supercedes everything else. In the first place they want to advance their careers, and make connections in order to advance into higher ranks of power and/or get well paid jobs in the private sector. What does voters prevent from voting for better candidates? Time and education. Because there is so much to check and understand (especially on topics that are even controversial among scientists), that it is simply impossible for ordinary people to do it. So most people go for the image of candidates and catchy key words and slogans (which is somewhat the political version of a "Back of the Napkin" calculation).

    34. Alex Wilson Pottery

      Microsoft's carbon neutral promise is pie-in-the-sky, as they announced it would require the use of technology that doesn't exist yet. 2030 is but ten years away.

    35. ibrahim abdusalam

      You should look into Andrew Yang, he's running for president and he talks about math all the time.

    36. Andy Lee Robinson

      This is pretty much how I've always done math and how I was taught in the UK so it is intuitive and obvious. It's some surprise then that this is news in America! Make Education Great Again! #MEGA

    37. bimmergeezer

      You obviously never seen me eat. The back of my napkin is wrinkled and greasy!

    38. Gordy Bishop

      The devil is in the details...hard to get all the details on a napkin. The napkin don’t have info like....corn grown from fuel uses more farmland and increases cost of food grown for human consumption....etc.

    39. bknesheim

      ref: 10:58 The b-roll that you use hear is really a good example for not using Napkin Math. The type of windmills and placement grantied that this would not work. Today the same math will tell you that the resources needed to replace coal, oil and gas with solar and wind garanty that this is not the answer. To replace a single 650MW gas driven generator you most install more then 2000MW off windmill and solar. If the cost is 1M US$ per MW then that would be 2B US$. Then add the cost off connecting it to the net. The math show us that we have only on type of tech that can replace fossil fuel and that is nuclar.

    40. kokoras12000

      You're right! #thunderf00t uses the critical thinking, you just described, to debunk the hyperloop!

    41. Nick Donley

      it's crazy how these guys think that you can make 3238 wind turbines in a year. Tesla has supply constraints do they think that the wind industry doesn't?. You will be severely bottlenecked by the amount of wind turbines a wind company can produce, crane companies that can construct, them as well as a technician's to keep them running

    42. Chris Avram

      Dont ignore the higher maths. Read about operations research/logistics and WWII. As for arithmatic, my firmative book in this area was Tha Mayor of Casterbridge. Book about a guy who knew how to workout how much produce was on a truck. Ie multiply LxWxH.

    43. Ulf Asplund

      Am I scientifically spoiled are people really not doing this? I remember growing up and my dad (who was a math professor), sat down at lunch breaks doing "back of the napkin math" that eventually turned out to advance n dimensional space math. I have always made my first business plans like this.

    44. Brian Eney

      Math illiteracy is my great pet peeve! People will gladly tell you “ I’m sorry I’m not a math person” and be OK with it! Conversely NO one will never admit they can’t read. These are the same thing! This country’s educational system needs to start treating tech is a tool- not your brain!

    45. Suzanne Wacan

      ehm...bit sidetracked..think its because you'r saying Math so much..but do you love Andrew Yang too?

    46. Lars Löwgren

      When Elon did the math they didn’t have any smartphones to search on...

    47. Gavin Faulkner

      The core critical thinking skill is not mathematics but the capacity to spot logical fallacies. Humans are particularly susceptible to confirmation bias, appeals to authority and appeals to emotion. I think this is where Elon succeeds. Anyone can learn to add and multiply but learning to spot logical fallacies is hard.

    48. Bob Lablah

      I wonder how long it would take to plant 2.2 trillion trees?

    49. Ross Ward

      Just because you have $9.7 billion dollars doesn't mean there are 350,000 people to install those wind turbines this year. (That's my back of the envelope math for how many people it takes to install a wind turbine.) There are maybe 35,000 people to install 350 turbines per year. Just sayin'.

    50. klebaer

      it woulnt even cost Microsoft so much money, because it is an investment und the wind turbines generates electricity which microsoft can sell... On the long run it the wind turbines pays für themselfs oder even generate an extra income...

    51. Blaise Dahl

      Take a shot every time they say napkin.

    52. robert tatum

      brillent !!

    53. po hu

      Why? An elementary student know how to do the math you are talking about.

    54. Rick Ash

      Your channel works, because you are "back of the napkinning" off each other the whole time. Great job and keep it up guys.

    55. Adam Wilkinson

      Just hurts my head hearing you Yankee doodles saying ‘Math.’ so much!! 😱’s MATHS!!!!! ...with an S! 😝 good vid tho 👌 Much love from the UK 🇬🇧

      1. Happs Tree Service

        Its Math here...much love from the U.S! For a field centered on numbers, math seems pretty confused about its pluralization. Americans and Canadians tend to say math while Brits and Australians opt for maths. ... Still, both versions are correct, if complicated by the fact that while mathematics sounds plural, it may actually be singular.... Thats google!

      2. Howdy Justice

        No, it is not.

    56. Miguel Angel Lozano Ortiz

      I recommend to Jesse and Zack this video

    57. Joel Herzog

      Just to play devil's advocate here. Things like flat-earth, antivaxx, and anti-climate change movements were created by unqualified people, using "back of the napkin math" then shared with a large group of people on social media. Rather than left to the scientists to properly test and get peer-reviewed before being published. I agree it's a skill people need to learn. And companies who need to make changes quickly need to use quick math and quick research rather than meetings and drawn-out processes. But some things should always be left to the proper methods.

    58. gfcgamer Orgone


    59. Wu Me

      Earlier I gave a shorter comment but I thought I should bring a longer worked example showing the sources I used. I subsequent learned I had also made an error in my calculations and have provide a more rigorous worked example as to why eating Ruminant animals is far better for the climate than Arable crop production given that its deposits 24Kg per square meter of carbon per annum as opposed to the increasing loses of carbon to the atmosphere, where we have lost 256Kg of carbon per square meter since the development of Agriculture. Please note that if we switched entirely over to meat over arable production we would sequester the damage caused by agriculture over the last 10,000 years in a little over a decade. "Grass not Trees. Grass captures carbon, ruminants eat the grass, the ruminants biome turns the grass into oils, urine and fecal matter, which the ruminant discharges and then pounds into soil with left over grass. 3 months later it can happen again. A cubic meter of top soil is 1600kg of soil. Approx 18% is carbon i.e. 1600kg x 18% 288Kg Carbon So to every year 288/12 kilogrammes of carbon is deposited i.e. 24Kg of Carbon So for every square meter of land how much carbon is deposited as a result of ruminants? 24Kg of carbon This is opposed to which states that "The annual rate of LOSS of ORGANIC MATTER can vary greatly, depending on cultivation practices, the type of plant/crop cover, drainage status of the soil and weather conditions. There are two groups of factors that influence inherent organic matter content: natural factors (climate, soil parent material, land cover and/or vegetation and topography), and human-induced factors (land use, management and degradation)." When looking at Arable food production states "Soil carbon, which correlates with the soil organic matter levels, was measured in 1981 and 2002. In 1981, the soil carbon levels were about the same (about 2%) in both the organic and conventional systems (Pimentel et al., 2005). In 2002, however, the soil organic matter in the organic systems was about 5%, whereas in the conventional system, it remained about 2%. The higher soil organic matter levels found in the organic systems cause the SOIL TO RETAIN MORE WATER that results in better crop yields during droughts, reduces soil erosion, increases plant nutrient retention and increases biological diversity...Higher soil carbon levels also hold soil particles together so less soil erosion occurs (Pimentel et al., 2005)." So how much carbon is retained in land used for plant food production A cubic meter of top soil is 1600kg of soil. Approx 2% is carbon i.e. 1600kg x 2% = 32Kg Carbon So for conventional arable food production we are seeing a loss of carbon in the soil so that instead of soil containing 18% carbon it typical retains 2%. So through conventional arable agriculture we have seen the loss of 288-32Kg of Carbon per square meter i.e. 256Kg of Carbon since agriculture began. And over time these losses will increase and becomes unusable for grow arable crops and eventually becomes desert an examle of which in Eygypt where once the nile delta was rolling verdant fields is now sandy desert due to human Arable Agriculture A useful source for measuring carbon content is So unlike arable crops that reduce the level of top spoil each year releasing carbon to the atmosphere. If we switched from eating Arable crops that are increase climate change to eating animals we would see a rapid end to climate change and a substantial & increasing lowering of atmospheric carbon levels. Unless this is a moral issue: that we should not be killing senient animal's to eat them for food? However, this would be a speciest argument since whilst eating Arable food means that ruminant animals are not eaten it actually increases thee number of animals and birds that are killed as farmers have to use pest control to stop sentient creatures such as birds, small mamals such as mice, rabbits, deer and other wild animals consuming their production. For example last year 30 million ruminats were killed for food in North America, meanwhile 66 billion bees died as a side effect of Arable food production. Meanwhile to make vegetables safe to be eaten by humans they have undergone massive genetic selection to reduce plants defences against being eaten by animals, bacteria, funguses etc So plants have been devloped that strip out some of the more deadlt chemical weapons that plants produce to protect themselves however this they then need to be protected by farmers through the use of external chemical weapons in the form of herbicides, fungacides, pesticides etc. The problem is that the use of these chemical weapons on the soil causes the soil biome to be destroyed, just as antibiotics kill our gut biome. The problem is that this goes directly against "Higher soil organic matter levels cause greater soil nitrogen retention, greater microbial biodiversity, and promote the presence and growth of arbuscular mycorrhizal fungi that penetrate the roots of crops and facilitate the movement of plant nutrients from the soil into the crop plants resulting in better crop growth and yields (Pimentel et al., 2005)." Also given the loss of organic matter from the soil and degradtion products from animal death such as blood and bone, there is an increasing need for artificial fertilizers derived from explosive production processes such as the creation of ammonia to create artifical nitrogen fertilizers. In the process this creates vast quantities of atmospheric carbon production. The problem is that artificial fertilizers are not as good as natural fertilizers for feeding plants, so that plants yeilds are sunstantially less as the plant has to work harder to convert the artificial fertilizer into something it can use

    60. Stefan Grabe

      Thank you guys ❣️👍🏽😃🙏🏽