It amazes me how defensive, threatened, and snarky people get about interview questions. When leading an interview, do you know how hard it is to tease out if someone is a creative thinker or just a bullshitter? Very hard. You come at it from multiple angles. Sometimes you need questions like this, it is part of the interviewing toolkit along with coding examples, and domain-specific challenges. EDIT: And sometimes y…
I thought it was a perfectly reasonable question to ask someone trying out for Microsoft's new manhole design division
How many ping pong balls would it take to fill a 747? Why do you ask? What problem are you trying to solve? We want to understand your thought process I'd think it was stupid to fill a 747 with ping pong balls and think about something else
Usefulness of the question aside, dismissing it as stupid is at the very least, shortsighted[1].
How many ping pong balls would it take to fill a 747? Why do you ask? What problem are you trying to solve? We want to understand your thought process I'd think it was stupid to fill a 747 with ping pong balls and think about something else
I don't get the derision for these kinds of problems. And I think it's unlikely Feynman would have found this unhelpful. These are commonly referred to as Fermi problems. Fermi was a physicist of Feynman's generation - they were probably standing together at Trinity when Fermi did the famous yield approximation. The other physicists held this ability in such esteem they gave it a name and remembered him for it.
The question is meant to gauge whether you can create a simple model of a system that is completely foreign to you, but for which you are familiar with the fundamental rules governing it. The absurdity of it serves to remove bias. You don't have to worry about whether or not the candidate happens to have experience filling airplanes with ping pong balls. So much of effective programming is creating a model for the processes we are trying to automate. Coming up with effective abstractions uses many of the same skills.
I'm not sure I buy this type of attack. How is this different from calculating yield of a bomb as Fermi did? It's back-of-envelope calculation that physicists do all the time. Ping Pong in a Boeing is merely a setup with the least context. This is like criticizing a math teacher for asking elementary students to calculate how long it takes to fill a swimming pool when water is flowing in and out of the pool at the sa…
This is fine if the question relates to something that the candidate is familiar with. But I have personally never set foot in a 747, much less be able to come up with any estimate of the dimensions in order to estimate volume. Then there is the formula to determine the packing volume of ping pong balls. Just like the question of how much water dumps out of the Amazon river per day. Yes, I can write down a formula wi…
I’ve found in interviews you can just declare your assumptions for the things you don’t know.
Ultimately these sorts of job interview questions are designed to evoke a response that can let you demonstrate how you would go about solving/explaining the problem; actually solving it correctly is rarely required or expected. I’d just say having never seen a 747, for purposes of the calculation let’s assume they are 300m long with a 10m diameter etc etc and proceed to do a terrible job of calculating how many ping pong balls fit.
I'm not sure I buy this type of attack. How is this different from calculating yield of a bomb as Fermi did? It's back-of-envelope calculation that physicists do all the time. Ping Pong in a Boeing is merely a setup with the least context. This is like criticizing a math teacher for asking elementary students to calculate how long it takes to fill a swimming pool when water is flowing in and out of the pool at the sa…
This is fine if the question relates to something that the candidate is familiar with. But I have personally never set foot in a 747, much less be able to come up with any estimate of the dimensions in order to estimate volume. Then there is the formula to determine the packing volume of ping pong balls. Just like the question of how much water dumps out of the Amazon river per day. Yes, I can write down a formula wi…
I guess we can always clarify the context? Something like: I've never set foot in a 747, could you please describe what that is? Can I assume that the plane has no furniture, and the dimension is yada yada? You know, have a conversation.
Actually, that's exactly what Feynman did in the excellent writeup: https://longnow.org/essays/richard-feynman-connection-machin.... A quote: "For Richard, figuring out these problems was a kind of a game. He always started by asking very basic questions like, "What is the simplest example?" or "How can you tell if the answer is right?" He asked questions until he reduced the problem to some essential puzzle that he thought he would be able to solve."
Ok, this is funny and odd. This immediately reminded me of the scene in Cryptonimicon where Waterhouse takes a 'simple' math test. It apparently reminded my past self of the same thing 11 years ago, when this was posted back then. https://news.ycombinator.com/item?id=1866629 (I dug up the actual passage from the book, so you can read it)
I listened to it as an audiobook while driving, and listened to that segment 3 times back-to-back.
How many ping pong balls would it take to fill a 747? Why do you ask? What problem are you trying to solve? We want to understand your thought process I'd think it was stupid to fill a 747 with ping pong balls and think about something else
I'm not sure I buy this type of attack. How is this different from calculating yield of a bomb as Fermi did? It's back-of-envelope calculation that physicists do all the time. Ping Pong in a Boeing is merely a setup with the least context. This is like criticizing a math teacher for asking elementary students to calculate how long it takes to fill a swimming pool when water is flowing in and out of the pool at the sa…
Why use the pool at all if you already have useful examples of inflow and outflow of money or another or the queue at the grocery store? Someone of age to understand flow rates of liquid would likely be able to understand money enough to be able to do the same calculations can’t get the same principles but with a functional analogy instead.
It amazes me how defensive, threatened, and snarky people get about interview questions. When leading an interview, do you know how hard it is to tease out if someone is a creative thinker or just a bullshitter? Very hard. You come at it from multiple angles. Sometimes you need questions like this, it is part of the interviewing toolkit along with coding examples, and domain-specific challenges. EDIT: And sometimes y…
I thought it was a perfectly reasonable question to ask someone trying out for Microsoft's new manhole design division
So that's why Windows sucks. It was designed by people who are good at manhole design, not writing software. :-)
How many ping pong balls would it take to fill a 747? Why do you ask? What problem are you trying to solve? We want to understand your thought process I'd think it was stupid to fill a 747 with ping pong balls and think about something else
The real problem with that question isn't that it's stupid. Everyone knows it's stupid, it's testing your ability to come up with an estimate in a domain you're not too familiar with using "napkin math". That's a legitimate skill and asset in software engineering. The real problem is that the ability to come up with a good napkin math estimate for a technical problem doesn't correlate with the ability to actually do…
Which is why companies started moving into other questions that have no relation to your job, like designing youtube. There is such a slim chance that you'll end up designing youtube at your tenure there, in a team of 2...that it's probably more likely to fill a jet with balls. Yet somehow people are not bothered by the design youtube question the same way they are about balls in a plane. It's true that the youtube version has technologies that are somewhat related to what you'll be doing, but in practice you won't have the opportunity to choose that many technologies for a single product, you'll be a cog in the machine anyway.
How many ping pong balls would it take to fill a 747? Why do you ask? What problem are you trying to solve? We want to understand your thought process I'd think it was stupid to fill a 747 with ping pong balls and think about something else
I don't get the derision for these kinds of problems. And I think it's unlikely Feynman would have found this unhelpful. These are commonly referred to as Fermi problems. Fermi was a physicist of Feynman's generation - they were probably standing together at Trinity when Fermi did the famous yield approximation. The other physicists held this ability in such esteem they gave it a name and remembered him for it. The q…
An interesting little tid-bit: I've read that Feynman was sitting in a truck at Trinity, and I think he was alone. Feynman calculated that the truck's windscreen would absorb enough of the bomb's UV emissions to obviate the need for additional eye protection. The same source (which I cannot currently locate) said that everyone else was wearing welding masks/goggles.