Hi,

How to approach the measure of Eiffel tower weight?

Thank you!

(edited)

expert

Expert with best answer

Hi,

How to approach the measure of Eiffel tower weight?

Thank you!

(edited)

3 answers

Remember, the key is to identify drivers, estimate the value, and use good judgement throughout.

Here's what I would do:

Assume the majority of the **weight **will be the metal structure, not the stairs or the screws or the concrete base. So we should focus on the **weight **on the metal.

**Weight = density x volume **for each "bar". **Density **we would look up in real life, but for now we have to make some assumption. So now we have to estimate the **volume **of each bar and the **number **of each bar.

**Volume **is the interesting part. **Volume is area x height**. For **Area**, let's assume that all "bars" are 1 square foot, although for sure some are more and some are less.

So we still have to estimate the **height **of the bars. How tall is the Eiffel tower? Maybe 300 metres? Maybe 1000 ft? So we can calculate the **volume **of each bar.

Finally, the **number **of bars. If I'm picturing it correctly in my head, we can say that the tower has 4 legs is made up of **4 vertical bars**. So total of 16 verticle bars, each 1000 cubic meters of volume.

There's probably also **diagonal bars**. Maybe assume that for each vertical section of 4 bars there are 8 diagonal bars (making an 'X' shape up each side of each leg. Assume they are like the hypotenuse of a right triangle so are approximately 1.4x as long as the height. So it would be the equivalent of 8 x1.4 ~11 for every 4 bars. So for the 16 vertical bars there will be 4 x 11 = 44 diagonal bars. Therefore 16 + 44 = 60 bars of 1000 cubic feet. There's probably also some **horizontal bars**, but let's assume these are thinner and negligable.

**Now, I just multiplly it through: 60 x 1000 x Density. **Assume **density **of 250 kg per cubic foot. Why 250? I'm trying to picture a solid cubic foot of steel and how many people it would take to lift it. If each person can lift 50kg, it would take 5 very strong people to lift, yeah that makes sense.

Okay, so 60 x 1000 cubic feet x 250 kg per cubic foot. So, multiply the last two terms first because it gives you a nice round number: 60 x 250,000 kg. We know that 6 x 25 =150. So 60 x 250,000 kg = 15,000,000 kg.

I'm trying to sanity check that, doesn't seem unreasonable.

Voila. That was fun. I have no idea if I'm right (or even in the ball park) but if I'm not, you can probably tell me which assumption(s) I made was incorrect, and fix it, which is exactly what is the point of a market sizing question.

Happy to help more, just message me!

Best,

Allen

(edited)

Hi there,

This isn't a brainteaser! This is a market sizing (though I know it doesn't sound like it)

__General Tips for Market Sizing__

- Just like in a case,
**make sure you understand the question -**what are you really being asked to calculate - Decide whether a
**top-down or bottom-up**approach is best **Figure out what you know you know, and what you know you don't know**, but could estimate- This helps you determine how to split out buckets

**Stay flexible**- you can start with a "high-level" market sizing, but gauge your interviewers reaction....if it looks like they want you to do more...then go along level deeper in terms of your splits

Hello!

This is a typical, not only with that building but, for instance, about the office you are in.

There are a bunch:

- The easy ones:
- Google it
- measure it in a picture where you have a referrence

- The difficult ones
- Measuring the shade at some point of the day and figure out the height with trigonometry

Hope it helps!

Cheers,

Clara