Google is your friend, as always. (Who knew?)
First, you Google "volume of a cylinder" to learn what the formula for a cylinder is, where the first page I see is:
http://www.mathsteacher.com.au/year9/ch14_measurement/18_cylinder/cylinder.htm
and the formula for a cylinder is Volume = pi * radius * radius * height
Since we may have all slept through high school geometry, we'll Google "radius", and Wikipedia helpfully reminds us that the radius is one half of the diameter (and gives us pictures, even).
http://en.wikipedia.org/wiki/Radius
radius = 13.5cm / 2
And, since we are assuming we all slept through high school geometry, we'll Google "pi" to find out what the value of pi is. We find:
http://math2.org/math/geometry/circles.htm
which tells us that pi is 3.141592
but we'll just use 3.14 to save ourselves some typing. Besides, the measurements in the review aren't all that precise. (For a calculation this crude, we could just use 3 as the value of pi and be plenty close.)
Then you plug in the numbers from the review, using radius = 13.5cm / 2 height = 25 cm
and
Volume = 3.14 * 13.5cm/2 * 13.5cm/2 * 25cm
We'll use Google to do the calculation for us (no scientific calculator needed), typing in
3.14 * 13.5cm/2 * 13.5cm/2 * 25cm =
and sure enough, Google does the math, figures out that you are using cm for dimensions, and gives you the answer in liters (kinda cool, huh?). Google says:
((((3.14 * (13.5 cm)) / 2) * (13.5 cm)) / 2) * (25 cm) = 3.57665625 liters
No text books, no calculator, no nothing. Just Google all the way.
If you have had your coffee today, you could do the same calculation in inches:
3.14 * 5.3in/2 * 5.3in/2 * 10in
which Google calculates and returns as liters:
((((3.14 * (5.3 in)) / 2) * (5.3 in)) / 2) * (10 in) = 3.61345413 liters
Presto! (Again.)
Since the stuff sack is not a perfect cylinder, but has rounded ends, you can assume that the actual volume of the stuffed MB Spiral is a little less than the full 3.6 liters, probably 3.5 or 3.4 liters.
Edited by marcclarke on 07/12/2010 12:23:47 MDT.
