Hi everyone!
Very, very, very low confidence – these are my two very first Fermi estimates ever; so Feedback will be very much appreciated.
q1:
Let‘s assume that every train station has ten rail tracks and that every rail track at a train station is ten miles long. That makes 100 miles for every train station.
How many train stations are there in the world – 10^6 (1.000.000)? Seems a bit low, let‘s go with 10^9.
So that‘s 10^2 * 10^9 = 10^11 miles only for train stations.
So how long are train rails that actually connect train stations combined?
Uh…
Let‘s assume that there will always be two train tracks for every connection (as for both directions, one track per each direction). Let‘s assume average length 100 miles for one direction.
How many connections are there?
Let‘s say 10^9 (I thought, it might make sense to have around as much connections as stations), so that makes 10^9 * 10^2 * 2 = 210^11 miles.
Together with our previous result that gets us
210^11 + 10^11 = 3*10^11 = 300.000.000.000 miles.
That seems a bit large, but hey… First try ever.
q2:
I have absolutely no idea, and so randomly guess 10.000 metric tons in 2009 and a 10% increase if we compare 2019 with 2009. That makes 10.000+1.000=11.000 metric tons for 2019.
Taking the average gives us (11.000 – 10.000)/2 = 1.000/2 = 500 metric tons as final result; at least if I interpret the task assignment correctly.
Congrats on making your first Fermi! You are taking the first step on and a long and rewarding journey of quantitative rationality :)
As for q1, claiming that the world has a billion train stations seems way too high to me. That would be enough for every two families to have “their own” train station. But when you look at the throughput of passengers there’s 1000+ at least per station.
I also think you’re neglecting the fact that train stations are connected to each other, and so end up double counting some tracks?
Hi everyone! Very, very, very low confidence – these are my two very first Fermi estimates ever; so Feedback will be very much appreciated.
q1:
Let‘s assume that every train station has ten rail tracks and that every rail track at a train station is ten miles long. That makes 100 miles for every train station. How many train stations are there in the world – 10^6 (1.000.000)? Seems a bit low, let‘s go with 10^9. So that‘s 10^2 * 10^9 = 10^11 miles only for train stations.
So how long are train rails that actually connect train stations combined? Uh… Let‘s assume that there will always be two train tracks for every connection (as for both directions, one track per each direction). Let‘s assume average length 100 miles for one direction. How many connections are there? Let‘s say 10^9 (I thought, it might make sense to have around as much connections as stations), so that makes 10^9 * 10^2 * 2 = 210^11 miles. Together with our previous result that gets us
210^11 + 10^11 = 3*10^11 = 300.000.000.000 miles. That seems a bit large, but hey… First try ever.
q2:
I have absolutely no idea, and so randomly guess 10.000 metric tons in 2009 and a 10% increase if we compare 2019 with 2009. That makes 10.000+1.000=11.000 metric tons for 2019. Taking the average gives us (11.000 – 10.000)/2 = 1.000/2 = 500 metric tons as final result; at least if I interpret the task assignment correctly.
Best regards, smiley314
Congrats on making your first Fermi! You are taking the first step on and a long and rewarding journey of quantitative rationality :)
As for q1, claiming that the world has a billion train stations seems way too high to me. That would be enough for every two families to have “their own” train station. But when you look at the throughput of passengers there’s 1000+ at least per station.
I also think you’re neglecting the fact that train stations are connected to each other, and so end up double counting some tracks?