"Annie and Evelyn observe that, on average, it takes approximately 10 days for a small glass of water to completely evaporate when left outdoors. What would they estimate for the average annual precipitation on Earth?" (Answer in depth of precipitation)(adsbygoogle = window.adsbygoogle || []).push({});

Here's my though process but I have a feeling it is a bit off, if you could help me out it would be greatly appreciated! Thanks!

Ok, so first I assumed that a small glass holds 250mL of water and is 10cm tall, and that all water that evaporates in a year falls in that same year, so the quantity evaporated = quantity precipitated.

So the Volume of the glass = 250mL = 250cm^3

Thus 250cm^3 = Surface area of the glass x 10(cm)

Thus the surface area of the glass is 25cm^2

So it takes 10 days for 250mL of water to evaporate from an area of 25cm^2, and thus in 1 day, 25mL of water will evaporate from that surface area.

Then i found the surface area of the earth, and took 71% of that (the part of earch covered in water) and found the annual evaporation of water. Then I spread that out over the entire earth's surface area to find the average annual precipitation in depth.

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# Homework Help: Very interesting estimation problem

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