Now is your chance! Here you get to find out how many feet of straw would go around the world and also how many gallons of water would fit inside a straw that was wrapped around the world! This is the product of extreme boredom… (Copywrite 2005 - Tyler C.)
And the moment you’ve all been waiting for:
(Can you believe I didn’t even do that on perpose?!? Whew, twice in a row…must be my old age…) Here it REALLY is!
heh…wowzers…that made me laugh.
How did you figure that 20 straws will hold 4 oz?
Did you measure the length and diameter then compute the volume? Or did you fill a straw with water 20 times, dump each straw full of water into a measuring cup and then measure how much water was in the measuring cup?
And what happens if you use straws from McDonald’s?
Come on John, this is one of his more valuable posts. Is his math correct? Assuming his starting figures are good numbers, which for our purposes should be good enough.
I did the water in the straw 20 times in a measuring cup thing.
Those are way bigger than normal, so it wouldn’t be the same.
WRONG. McDonalds straws are barely bigger in any way, however, due to that chaos theory, yes the final result would be much much bigger!!! CHAOS THEORY!!!
I think its pretty cool (?) the way you start out with 1-2 significant figures, and end up with like 16! I tend to do the same thing, so that if I use it for any other calculations, it will be as accurate as possible 
Yes, failing to keep all the extra digits in the memory of the calculator will cause the final answer to be off by a little bit. Case in point, the final result is actually 318088.01117578064516 gallons of water per Earth diameter sized straw if you carry out the decimals a little bit farther rather than truncating them when you write them down from the calculator display. Can’t let those extra digits go to waste.
I declare Tyler’s answer to be incorrect because he blows it at the 5th place after the decimal point.
if you “add” significant figures you’ll be less precise. well, put another way: you won’t know how far you might be off. granted if you measure something to the milimeter and it comes out to be 1 meter, you don’t just have 1 sigfig, you have 4. One for each digit in the 1000 mm in one meter.
The easier way to do those types of calculations involving lots of unit conversions is to write it out as a series of ratios with the correct units all multiplied together and cancel out all the units till you’re left with what you want.
It’s much easier to keep the units straight when you do the calculation this way.
For this straw problem you would end up with a calculation like this:
I was always taught (in maths & physics) that you should always discard significant figures (or decimal places) beyond the maximum accuracy of your initial values. So since tylers lowest level of accuray is 2 d.p (the straw length) his final figure should be quoted as 318088.01. I think its to stop you from ‘inventing’ accuracy, or something.]
lol, gallons per earth_diameter, thats a classic unit.
Did you know the speed of light is 1.8x10^12 Furlongs per Fortnight? I love that unit.
Loose.
It’s the circumference of the Earth, not the diameter. Tyler was talking about a straw long enough to go round the Earth, not through it.
Also, I believe I’ve heard that the earth has a bigger circumference around the equator than it does north to south. Which way are your straws going to lay? Also, if you lay them north to south, then you’ve got to figure in expansion of the water when it freezes at the poles.
Re: Ever wanted to know how many gallons would be in a straw around the world?
Tyler,
Be sure to copyright your work.
i still dont understand how you figure out how much water could fit in a straw, did you like make a little stray lid or what?
Yea, JC, I’m a unicyclist not a pogo-sticker!
Since a person who rides a unicycle is a unicyclist, wouldn’t a person who rides a pogo-stick be a pogo-stickist?
Actually, that’s not how significant figures work. His measurement of the straw has three significant figures in it, therefore his answer should have at most 3 sig figs too, so it should be 318000
Now, if you quote the uncertainty in a measurement; say the length is 7.75 +/- 0.05, then that can change things again. You would then propagate that error through the calculation as a relative error, 0.05/7.75 and add up the relative errors, RMS (root-mean-square), to get the uncertainty in the final number.
Damn, I shudda been a perfesser.