A credit card company just sent me the attached "useful tip." In particular, check out this scenario and its illustration:
"Here's an example of what a $750 purchase could cost you over time based on a 14.90% interest rate...."
The accompanying pictures seem apropos to consumer purchasing ... except that bags introduce the third dimension of possible interpretation that Robert Hansen warned about earlier in this thread. (It turns out that the percent increases in price most closely correspond to the changes in the linear measures rather than to those in area or volume -- likely an artifact of the kind of intuition you've hypothesized, playing out with the tools of desktop publishing -- all of which reminds me of a conversation taking place in another discussion: http://mathforum.org/kb/thread.jspa?threadID=2085759 ...).
Moral: even those who invest heavily in their education to make it their business to count beans still only ever count them in a row.
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