Simple math errors seem to get published so often. I've run in to three today.
First a post on another thread quoted an article about how if we reduced our nuclear arsenal to 311 warheads we would still have "the equivalent of 1,900 megatons of explosive power". When the reality is it would be less than 150 megatons, maybe less than 100. (See more here Message 26560311 ). I suppose this might have been a mistake in knowledge about the yield of our warheads, but if so that's just as bad IMO. Don't be precise ("311 warheads" are needed, not 300 or 350) if you don't know what your talking about. And the article was written by an "assistant professor of strategy at the Air War College" and a "professor of strategy at the School of Advanced Air and Space Studies", so you would think they would know something about nuclear weapon yield.
Then I was reading a Reader's Digest from last year. They quote Cnet as saying 90% of mail is spam, and say that means for every 1.1 e-mails 1 would be spam, but 90% means for every one e-mail .9 would be spam (more commonly stated as 9 out of 10 would be spam). 1 out of 1.1 isn't 90% its about 91%. At least this error isn't a large one like the one in the last paragraph.
Then I read the following blog post -
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The Wall Street Journal's Math
David Henderson
In today's Wall Street Journal, one of the editorials makes the following statement:
Arizona got into this crisis because during the boom years--2003 to 2007--then-Governor Janet Napolitano, a Democrat, and Republicans in the legislature let spending climb by more than 100% to $10 billion from $6.6 billion.
Of course, the increase was 52%, which is distinctly less than 100%.
But how did the Journal's editors make this mistake? I think it's because they've succumbed to the incorrect modern usage in discussing increases. Here's an example:
GDP in a poor country rises from $10 billion to $40 billion. The modern usage is that it "rose fourfold." But it didn't. It rose threefold. When I've made this point to my students, I've pointed out that when a number rises from 50 to 90, by the modern usage one would say that it rose 1.8 fold. But it didn't. It rose 0.8 fold.
I was wondering when I would first see someone make the error that arises from using the modern usage consistently. I just did.
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