Help me find an online surface area/volume calculator that uses 3.14 as an approximation for pi.

November 5, 2009 8:34 AM

I'm looking for an online surface area and volume calculator, where I plug in various measurements of a cylinder or sphere and it calculates the answer for me. But I want one that approximates pi as 3.14.

No, you're not helping me to cheat. I'm answer checking middle school math materials. All the surface area and volume calculators I've found online use a much longer approximation of pi, and all the questions I'm working on specifically direct students to "use 3.14 for pi".

(Note: if your answer includes any variation on "It doesn't take that long to calculate the surface area or volume yourself", then you are an unhelpful person who isn't very good at reading.)

posted by 23skidoo to education (8 comments total)

I would use excel for this. It'll take 3 seconds.
posted by dmd at 8:37 AM on November 5 [1 favorite has favorites]

Agreed with Excel.
posted by dfriedman at 8:38 AM on November 5

I would use excel for this. It'll take 3 seconds.

I have no idea how to make excel do this, so if you could explain exactly what to do, I'd appreciate it.
posted by 23skidoo at 8:40 AM on November 5

Hold on, 23skidoo - I'm making a google document to do it, which you should be able to access from anywhere with a google account.
posted by muddgirl at 8:44 AM on November 5

OK, hopefully this works: Area and Volume calculations for sphere and cylinder. Just go to the correct sheet and enter the height and radius. You can even change Pi to whatever you'd like, although I defaulted it to 3.14. If the problem gives the diameter, just divide by two and enter the radius value.

If you double-click on the answer cells (highlighted in yellow), you can see the formula used to make the calculation and make changes if you like. A formula has to start with an equals sign "=" and anything in the format A2 or B12 indicates that the formula is taking a value from the cell in Column A row 2, or Column B row 12, etc.
posted by muddgirl at 8:55 AM on November 5 [1 favorite has favorites]

Also, it just occured to me that any malicious person could come along and edit the sheet to give the wrong answer, so if you'd like, I can lock it down and send you a private link by email/memail. Or, I think if you have a google account you can save a private copy to your own Google Docs folder and you will be the only one able to edit it.
posted by muddgirl at 8:59 AM on November 5

Thanks, muddgirl. I'll figure out how to save a private copy to thwart any shenanigans.
posted by 23skidoo at 9:13 AM on November 5

Have you tried Wolfram Alpha? It looks like it will round for you.

volume of sphere with a radius of 5cm
posted by blue_beetle at 10:54 AM on November 5