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Via Jonathon Scwharz at A Tiny Revolution, we have this...
...with the comment, "If you figure out how old the father and son are in this cartoon (found here), it actually shapeshifts from something depressingly unfunny to a small masterpiece of alarming creepiness." The link in the quote will take you to the source of the above, and the link above the comic will take you to the answer. I actually took a little bit of pleasure from dusting off my badly unused algebra skills and working this out for myself; it went quickly. Sad to say, this is the kind of problem I used to solve in my head in a few seconds. Now I have to write it all down to make sure I'm keeping everything straight. As for the first picture, I grew up with "New Math" and that sort of problem was what we were doing in first grade, albeit with an empty box in place of "X." So by the time I got to "actual" algebra in 9th grade, it seemed second nature.Hint as to why the answer is sort of deliciously creepy: think Michael Douglas and his more recent progeny in 10-15 years.
Followup: As long as we're on the subject of stupid math tricks, today is international palindrome day, 01022010. Via Pygalgia (where I saw it first), among others.
I'm sorry, but I love stupid things like that. I also like oatmeal. Which is probably weird.
ReplyDeletePygalgia- Absolutely no slight intended! "Stupid Math Tricks" was one of the very first labels I started using, here:
ReplyDeleteI do want to point out that these "stupid math tricks" that I will spend occasional time discussing are neither "stupid" nor simply "tricks." I chose the word trick because, really, who doesn't enjoy knowing a few "magic" tricks? I don't consider these procedures just "tricks" because they can, on occasion, be very useful. In the context of one of my undergrad lab jobs, people got into the habit of calling out arithmetic problems to me. ("Hey, if there's .54 grams of carbon in a 6.2 gram sample, what's the percent C?" "Well, umm, about 11 and a half.") I'm convinced this got me a couple of raises. I could generally answer within a few seconds then, though due to lack of practice and an aging mind, I'm slower now. It's partly the lack of practice I want to compensate for now, but mostly I want to pass on the tricks. They're simple and easy to pull off inside your head, without looking for the nearest calculator, and they can truly be useful. I want to encourge people to be facile with math and arithmetic.
I chose the word "stupid" first to make the topic seem a little less threatening (these tricks are easy to use), and second as an allusion and homage to Letterman's stupid pet tricks- which were often quite amazing. Just as some of the stupid math tricks are.
The label is intended to be more of a sneaky comment to get people to pay attention to math that they might otherwise skip over. (In other words, I love stupid things like that, too. I also like oatmeal, though just between you and me, I like Cream of Wheat even better.)
Also (he admits with a grin) the whole reason I started this blog when I did was to share a stupid math trick I had figured out for myself.