We want to assess a list of vendors in two domains: Accessibility and Cost. We have two tools that we are using to essentially score them in each of these domains separately. The Accessibility assessment tool totals 110 points; the Cost tool totals 90 points. We want a final score for each vendor that combines the domains and is out of 100. We want the Accessibility score to "count" about 20% more than the Cost score in the final because it is more important to us. How do we do this? [more inside]
posted by OmieWise on Mar 14, 2013 - 10 answers

Harmonic or Arithmetic Mean?: I'm trying to settle an argument with my wife - is using the arithmetic mean or harmonic mean more appropriate when finding the "average" number of, say, online comments made by a large number of people, where a significant portion of them make only one comment and a few people make the bulk of the comments? [more inside]
posted by salsamander on Jun 2, 2012 - 13 answers

Basically, what it says. I've been brushing up on my math skills via Khan Academy, and I'm running into a problem I hit when I was in school. Basically, the math *concepts*, like Algebra, Trig, and the like? I'm able to get really easily. But, manipulating the numbers and doing the basic arithmetic? Hard. Sometimes even with a calculator, I'll miss carrying over a negative sign, and I'll get the problem wrong, despite knowing the concepts really, really well. What's going on here? Is my ADHD not under control? Are these symptoms of Dyscalculia? What? Ideas, hivemind! [more inside]
posted by spinifex23 on Mar 10, 2012 - 28 answers

What is the difference between floating point accuracy and precision?
posted by conrad101 on Jan 2, 2012 - 10 answers

I've seen people compute complex arithmetic off the top of their head. How do they do it? [more inside]
posted by Christ, what an asshole on Apr 30, 2009 - 13 answers

ABC x D = BADC. What single numbers (1-9) do the letters represent? Is there any way to arrive at the answer (a) by logical deduction all the way rather than with some trial-and-error and (b) so that a 10-year-old can follow the logic? [more inside]
posted by londongeezer on Sep 16, 2007 - 15 answers