Caution!

This is in a textbook:


calculus caution


CAUTION!
The area of a washer is pi*R^2-pi*r^2, which you can simplify to pi*(R^2-r^2), but not to pi*(R-r)^2. No matter how tempting it is to make the latter simplification, it’s wrong. Don’t do it.

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Free time graph


free time graph

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The average person has one testicle and one ovary…

The first one is how to cheer up your friend…


spiked math one testicle comic




Just don’t tell him he should have one ovary :P

statistics show one testicle and one ovary


This actually appeared in a textbook…

yahoo answers fail

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Addition Fail

addition-fail.jpg

Link: http://www.youtube.com/watch?v=VTNXlHY7YSk
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Deck Shuffling


shuffling a deck of cards

Cool fact: If you thoroughly shuffle an ordinary deck of 52 playing cards, chances are that the resulting arrangement of cards has never existed before (via Reddit and Reddit).

Quoting from the math subreddit:

Proof — easy numeric comparison. There are 52! possible orderings of a deck, and I’m assuming all are equally likely after your shuffling. Let’s wildly overestimate and assume that every second since the universe was created, a million decks of cards were shuffled and someone looked through them. Thus fewer than 10^24 orderings have ever been seen.

But at an incredibly crude estimate, 52! is at least 10^42 * 10!; let’s underestimate that again wildly by 10^42. That means that chances of your ordering ever having come up previously are at most 1 in 10^18.

(Note, by the birthday paradox, the chances that there have been two identical orderings observed by two people in history are quite a bit higher — perhaps even feasibly likely; I haven’t calculated it. But we’re looking here at the probability that a given ordering matches one of the ones previously seen.)

Discussion here.

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how girls/guys rate guys/girls


rating boys vs girls

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Color-blind Rubik’s cube solver

This is cute ^_^


colorblind rubiks cube

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Short math joke

∀∀∃∃

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Comcasts needs it’s -$0.05

This is pretty funny (via the consumerist).

Comcast sent a letter to this guy named Aaron demanding he pays -$0.05 to avoid interruption in service.

5cents.jpg

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Math vs Sex (graph)

This is old but curious nevertheless:


math sex graph


The y-axis is % of majors that are virgins
The x-axis is of course the student’s major.

Seems that Wellesley College is an all-girls college? Some insight into the origins of the graph.

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