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# Main Writers Cannot Do Math Discussion

Lenoxus
Topic
09:11:44 PM Jan 22nd 2017
I don't understand the Mean Girls example. -4 times -6 results in a positive number, 24, right? The only possible inaccuracy I see in that dialogue is Aaron saying the product of two negative numbers is sometimes positive, when it always is. Also bringing up particular numbers like that is a bit peculiar, but not wrong.
depizan
Topic
12:38:53 PM Aug 15th 2015
Am I missing something about the Seventeen Again entry? It's possible to be 19 and a high school senior, or at least to turn 19 the year you graduate. (Never mind the possibility of people being held back a grade...if they still do that.)
W3irdN3rd
Topic
01:59:35 AM Jun 29th 2015
Does someone know the context for that Superman Super-mathematics comic panel? It appears he just guessed the weight of the jar (he doesn't know the weight of an empty jar), meaning he can't possibly measure the number of beans accurately. I already added that to the note, but I want to remove the "seemingly". For all I know he might have checked the weight of an empty jar in the previous panel, although "allowing two pounds for the jar" sounds like guesswork.
MyFinalEdits
08:26:35 AM Jun 29th 2015
All that matters for the trope is the math, the numbers, not the methodology. So I'd say we shouldn't speculate about that "guessing".
W3irdN3rd
10:54:50 AM Jul 2nd 2015
Good point. Although he does pretend to be capable of providing an exact number using math, which he just can't not knowing the weight of the jar. Even if his math were correct, there would still be no guarantee the number is accurate.

That part is perhaps another trope, I'm not sure which one that would be. If you do perfect math but you're using rubbish for input, what would that be?
MyFinalEdits
07:16:03 PM Jul 2nd 2015
I can't think of anything, but you can ask at Lost and Found. =)

In any case, since Superman is a superhero, perhaps he does have some magical methodology to measure weight (even if the numbers may not be correct).
Racnoss
Topic
09:46:52 PM Dec 7th 2014
This example from Harry Potter:

"As class is an hour long, and they start at 9:00, there probably shouldn't be two classes, a break, and another class before lunch, as the break seems to be at least thirty minutes, possibly an entire hour, and logically pushes lunch to at least 12:30. Then there are a break right after lunch, two more classes, and then free time until dinner. It's not mathematically impossible, but it is a strange schedule, to say the least."

The description of the school day (apart from a longer morning break) could equally well describe my schedule at school. I don't understand what the OP found sound strange about it. I was hoping someone could provide some insight.
SeptimusHeap
03:17:08 AM Dec 8th 2014
Seems like nitpickery to me. I'd be OK with removing such an entry.
Sultanbruno
Topic
06:23:38 AM Mar 29th 2014
In the Recess example, the claim is that each kid would only get \$17 if \$100 were split six ways, and yet they each fantasize about buying lots of extravagant things with their share. That is definitely a mathematical error, but it may be justified in that fourth-graders do not often have a good sense for how much things really cost.
MyFinalEdits
11:47:26 AM Mar 29th 2014
Is it explicitly shown that they plan to split the money?
LordGro
Topic
01:14:20 PM Nov 26th 2013
Removed this example and natter. Not sure if it is an example, but if it's merely a joke meant to be obviously incorrect math, then it probably doesn't count.
• In Gilbert and Sullivan's The Sorcerer, Sir Marmaduke brags that he can trace his family back 7,000 generations, all the way to Helen of Troy. Considering that Helen of Troy was around 3,000 years ago ...
• This is probably more a mistake of the character than the writers. They loved mocking the grandiose claims of British nobility. In The Mikado, Pooh-ba claims he can trace his ancestors back to the very first "protoplasmal primordial atomic globule."
qetuos
Topic
12:00:45 PM Aug 7th 2012
In the superman example, 32,000(number of beans according to superman)/(20(beans per ounce)*16(ounces per pound))+2(weight of jar)=32000/(20*16)+2=32000/320+2=100+2=102 pounds.
MikeRosoft
Topic
12:48:03 PM Aug 4th 2012
edited by MikeRosoft
Removed for filling the page with natter:
• The Bible makes the case that π=3. Twice. Both 2 Chronicles 4:2 and 1 Kings 7:23 describe the building of a large water tank that is 10 cubits (30 feet) in diameter, with a circumference of 30 cubits. An accurate approximation would put the circumference at about 31-1/2 cubits.
• However, if we take into account that the bowl was said to be 1 handbreadth thick (appx. 1/4 cubit), and then assume the diameter given is the outer diameter (10 cubits), and the circumference given is the inner circumference (30 cubits) we can calculate the circumference over the diameter to be about 3.16, which is close enough considering all units given were whole numbers and the measurement tools of the period were ropes with knots in them.
• The Gospels of Luke and Matthew both list the genealogy of Jesus, leading back to King David. However, they don't match, featuring several discrepancies. A number of explanations for this have been suggested, but this trope comes in where one lineage is 41 entries long and the other is 77 entries long, which, while not impossible, would be very unlikely even if we assume one lineage is Marys and one is Josephs, or if we refer to Josephs lineage by starting with his biological father or hypothesized 'legal' father in the different versions.
• This particular one can get complicated. The one in Matthew was supposed to be partial. The one in Luke is supposed to be complete.
[MR: Says who? The Matthew's genealogy says: "Abraham begat Isaac" etc. - "begat" means "was the father of".]
• The story of Noahs flood lays out the exact size of the ark, at 30x50x300 cubits. While pretty big for a boat (approximately the size of the Titanic, going by a cubit being roughly equal to a yard), this boat had to fit at least two of every animal and seven of some other animals, as well as all of the food necessary to keeps its passengers alive for the whole duration. Possibly justified if God worked some miracle to make the Ark bigger on the inside.
• Assuming 1 cubit is equal to one yard, that leaves the Ark with 450,00 cubic feet, more if the long cubit is used. Most animals are not larger than a sheep, especially in the juvenile stage. The writer might not be as off as you think.
[MR: Er? A cubit is about half a meter; plus, the largest wooden boat built was smaller than the Arc and needed to be constantly pumped due to leakage. But there's little point in haggling about numbers in a myth; you could just as well make a detailed analysis of why it's scientifically implausible for The Flash to rescue half a million people in a fraction of a second by moving at near the speed of light.]
MetroRanger
Topic
05:29:00 PM Jul 26th 2012
Just spotted a problem with the following,

"People tend to be predominant in one hemisphere of the brain - the left hemisphere is for logical faculties such as math, and the right hemisphere is for creativity. So it follows that those with a well-developed right hemisphere will be good at writing but poor at math. This extends to artists and musicians as well, although there are exceptions."

That claim about the brain hemisphere is wrong (Obviously did not do the research) - While it is true the brain is split into two hemispheres, they are largely symmetrical and serve the same functions. There are limited examples of hemisphere localization (ie, Broca's and wernicke's areas) but it certainly does not work as the split-hemisphere myth argues. Almost all higher-order thinking (Creativity and logical/analytically) is processed in the frontal lobe, just behind the forehead, in both hemispheres of the brain. Studies with split-brain patients (where the hemispheres a split by cutting the neurofibres that connect them) show that both hemispheres of the brain respond to creative, emotional and analytic problems.
Michael
Topic
07:14:42 AM Jul 8th 2012
The Werewolf: The Apocalypse example misses the fact that kinfolk, who greatly outnumber werewolves, do have a chance to produce their own werewolf offspring. That seems to be where the missing werewolf population comes from.
DocJayden
Topic
10:05:57 AM Apr 15th 2012
Another one of David Weber's goofs (From the 12th novel of his Honor Harrington series, "Mission of Honor".

Verbatim quote, from the part dealing with the aftermath of Oyster Bay:

"Against all that, less than nine thousand treecats might not seem so terrible. But there were many planets occupied by human beings, while by the Sphinx Forestry Service's best estimate, the total treecat population was probably less than twelve million, which meant those nine thousand lives represented almost a full percent of them. Not one percent of the treecats living on the planet Sphinx one percent - one out of every hundred - of every treecat in the entire universe."

According to the above, somehow, 9000 treecats is 1% of all treecats in the universe (including those on Sphinx), and yet is barely 0.1% of the treecats on Sphinx itself.

On the other hand, this seems to be consistent with the mathematical laws of Honorverse...
Khantalas
Topic
10:14:42 PM Mar 4th 2012
Under webcomics, what makes the Schlock Mercenary example an inversion? Would not an inversion be Mathematicians Cannot Write, and a writer being able to do math be an aversion of the trope instead?
EnragedFilia
Topic
04:06:00 PM Sep 15th 2011
With regards to the example

• If there are only 3000 wizards in all of Great Britain, how do they have such a sprawling governmental bureaucracy? There wouldn't be nearly enough tax revenue for what we see, not even close. Unless the entire Ministry isn't getting paid...Also makes you wonder how the economy works. How do the Malfoys have so much money? We never see their business, and there really aren't enough consumers for anyone to get very wealthy. It could be mostly inheritance, but that just pushes the issue back a few generations.

I had always presumed that at least part of the real-world, muggle government was aware of the 'wizarding world' and helping to maintain the Masquerade. The whole issue of Potterverse economics becomes much more complex and thus easier to handwave if the magical and muggle economies coexist.
Topic
03:39:43 PM Apr 23rd 2011
I deleted the Kelly's Hero's example, as the statements it made are erroneous, when the numbers and evidence as given in the movie are used.

Here's the deleted example:

• In Kelly's Heroes, the number of gold bars stated in the heist is 14,000. The initial value of the stolen bars was estimated at \$1.6 million and then later corrected to be estimated at \$16 million in total. The international standard weight for gold bars is 400 troy ounces and in 1944, the price of gold was \$35 dollars per (troy) ounce. That would make approximated total value of the score to be closer to \$196 million dollars; not \$16 million dollars as stated. Also, 14,000 gold bars, valued at \$16M, equals about \$1,143 per bar. At the long-standing price of \$35/troy ounce, the bars would have had to weigh only 32.6 oz (almost 36 oz avoirdupois) each—probably a gross understatement, even though the bars are clearly much smaller than the standard "Fort Knox" size. But even assuming the weight is correct, 14,000 bars would weigh almost 16 tons (not counting boxes, men and equipment)—well beyond the capacity of the truck they were using. Then again, 14,000 bars, at only 12 to a box, would require over 1,100 boxes—seemingly a lot more than is in the pile.

Taking the statements individually:

• "The international standard weight for gold bars is 400 troy ounces"
• That's the standard "Good Delivery" gold bar held as reserves by banks and governments. Each reserve bar weighs roughly 27 pounds (avoirdupois). That's clearly not what these were, considering that neither the Nazi courier nor Kelly or anyone else has any problem picking up or carrying one one-handed, nor do they have any difficulty moving boxes that contain 8 of them (which would weigh at least 220 pounds if they were the Reserve bars) The bars in the movie were "transport" bars. These are most often what are called "kilobars" — 1000 grams, or 2.2 pounds avoirdupois, or 32.15 troy ounces — and if so, at \$35.00 per troy ounce, each bar would be worth about \$1,123.50.

• "in 1944, the price of gold was \$35 dollars per (troy) ounce"
• That was the US price. Crapgame is working with the Paris free market price, which could fluctuate somewhat, although it would have been near USD \$35. per troy ounce. This is further supported at the end of the movie, when Crapgame is quizzing Wilson; he gives the value of each box of 8 bars as \$8,400, or \$1,050 a bar. Either the bars are a bit short of a kilogram, or the Paris price for gold wasn't exactly \$35.00 per troy ounce. Or both.

• 14,000 bars would be worth "closer to \$196 million dollars".
• Presuming they were transport kilobars, and that the gold price was \$35 per troy ounce, 14,000 of them would be worth \$15,729.000. That's certainly close enough to \$16,000,000 to count.

• "14,000 bars would weigh almost 16 tons (not counting boxes, men and equipment)—well beyond the capacity of the truck they were using."
• That would be true, if Kelly's group was taking all of them. But they aren't. The deal offered to the Tiger commander is "an equal share"; Crapgame later states that "After splitting with Oddball and the German, we should have 125 boxes left." It's safe to assume, from the shots of the box they break open and the way the various men are carrying them, that each box has 8 2.2 pound bars, and weighs around 20 pounds, allowing for the weight of the box itself. The truck, therefore, is carrying not 16 tons of gold and boxes, but 2500 pounds, 1.25 tons'' of gold and boxes, easily within the capacity of a truck that size, even with the 12 remaining men and their gear.

That's not to say that all the math stands up; it doesn't. At eight bars to the box, there should be 1750 boxes, total, and after splitting with Oddball and his four remaining crewmen and the German (only the tank commander gets a share; his four crewmen are SOL; this follows from the fact that dividing 16 million by 875,000 yields 18 shares), there should be 1167 boxes left — 97 for each man. But The Law of Conservation of Detail and the Willing Suspension of Disbelief now come into play: With the tension building as the General approaches and enters the town, the accuracy in math is sacrificed because 10 men (first there's a lookout posted on the edge of town, then Big Joe goes to talk to the mayor; and Crapgame is out of commission with a gunshot leg) wouldn't be able to load that number of boxes in the time remaining. Oddball wouldn't be able to fit nearly 500 boxes into the tank. The number of boxes was scaled down by a factor of ten to make the story work better.
50.46.223.99
Topic
07:42:55 AM Mar 22nd 2011
In the reference to Harry Potter, the entry assumes that Nearly Headless Nick and Nicholas Flamel are the same person (hence the mistake in age). They are not.
muninn
Topic
02:10:10 PM Sep 5th 2010
Removed this:

• According to the K-On! DVD box set Yui's birthday is November 27, while her younger sister Ui, who is one class below, was born on February 22. This must mean that they are either three or fifteen months apart, and in the latter case they should be two classes apart instead. See the show's Wild Mass Guessing page for several theories as to how this might work.

15 months apart and 1 grade difference is only impossible if the cutoff date for enrollment is somewhere between the end of November and the end of February. The japanese school year starts in april.
HonoreDB
Topic
08:15:13 PM Aug 21st 2010
Okay, it seems no matter how many Weasel Words and caveats I add to a Bible entry, it's still going to get deleted as, well, blasphemy. I don't want to get into an Edit Crusade or anything, so I'm just going to note that this really should be on the main page for this trope:

• Two passages in The Bible infamously seem to imply that π=3, although there are plenty of ways around it if you believe the book to be inerrant.

Here's one of them. If you're an unbeliever reading the text as an artifact or as literature, this just looks like the author didn't know about π. If you knew that the ratio of a circumference to a diameter is constant, you wouldn't bother to say what the circumference of a circular object was if you'd already given the diameter. If you were to give the circumference just for emphasis, you wouldn't round down, since you're multiplying by a mathematical constant not a rough quantity (same reason you never say that half of thirty is ten, it just looks wrong). Now, I realize that reading the text under the assumption that it's completely flawless and divine means you look for a different explanation (the most creative one I've seen is that "rim" refers to the inner rim, and the bowl has a thick lip) and are at any rate confident that one exists. But by that standard none of the examples on this page should be here, since you can Fan Wank any of them if you want to to be Watsonian.
70.174.66.35
07:51:14 PM Nov 3rd 2010
edited by 70.174.66.35
It's not an example because the Bible isn't talking about something fictional that they got the numbers wrong about.

2 He made the Sea of cast metal, circular in shape, measuring ten cubits from rim to rim and five cubits[b] high. It took a line of thirty cubits[c] to measure around it.

He MADE... This thing was actually built, and actually had those measurements. The value of Pi has nothing at all to do with it. How these measurements were arrived at is what is disputed. There's the inner rim/outer rim theory, the general biblical trend of estimation, the cubit being a nonstandard measurement...the point is that there is no lack of math skills by the author of the Bible on display here.
HonoreDB
01:27:31 AM Nov 4th 2010
If I understand correctly, you're saying that the Bible isn't saying "it was thirty cubits" but "it measured thirty cubits," and therefore it was just quoting somebody else's measurement, not making an assertion about reality. That seems like just another Fan Wank to me, and it doesn't really change the main point: describing both the diameter and the circumference of a circular object is a math-ignorant thing to do, even if you're quoting someone else. It's as though a book said: "Ernie calculated that 37 times 11 was 407, and also that 11 times 37 was 407." Whether or not that's an accurate account of calculations Ernie made, it makes it look like the author doesn't know that x * y always equals y * x.

I don't know where you're getting "this thing was actually built" from...I'm pretty sure there's no account of it outside the Bible.
fakeangelbr
03:36:45 PM Feb 3rd 2011
edited by fakeangelbr
You know, the value of pi wasn't measured as is today, it was a very gradual process.
It might be possible that by the time it was written, pi=3 was in fact considered correct
HonoreDB
12:13:07 AM Feb 4th 2011
Sure, then it would be Science Marches On. In this case, though, pi was calculated out to several places by ancient Greek geometers, and there are documents that use it from around the time and place the relevant books in the Bible were written.
78.105.234.201
04:47:47 AM Feb 27th 2011
Er...The passage says "circular" not a perfect circle. Sightly elliptical objects are still circular
Wardog
03:51:11 AM Aug 20th 2011
The simplest explanation would be that the measurments are only given to the nearest whole cubit. A 9.67 cubit diameter disc would have a circumferance of 30.38 cubits. Rounding that to 10 and 30 seems quite reasonable to me.

Coversely, saying "He made the Sea of cast metal, circular in shape, measuring nine and sixtyseeven hundredths of a cubit from rim to rim and five cubits high. It took a line of thirty and thirty eight hudredths of a cubit to measure around it" would be horribly cludgy, and wouldn't provide any more useful information in a passage which is really just Scenery Porn rather than making an important theological or historical point.

(For what it's worth, I'm an atheist, so I don't have any great reason to defend the Bible. But criticising this particular passage seems to me to be unjustified)).
DanaO
Topic
12:18:44 AM Jul 18th 2010
We're sure about the Bleach example? While it's clear the author didn't do the math, the end result could still be sound. To extrapolate the effects of a drug at a certain dosage from its known effects at another is often unreliable, and even when there are scaling effects the scale is rarely strictly linear. In the real world, we still need some trial and error to determine what dosages actually do. Granted, the setting allows that Mayuri's drugs can behave like energy rather than matter, so they may not behave as per reality.

As a side note, if you take the latter approach, assume there are a specific number of the drug's "spirit particles" dispersed evenly throughout the subject's body, and make the (oversimplified to the point of stupidity, but...) assumption that the effect's intensity is based on the mean distance of the subject's "spirit particles" to those of the drug - in other words, something resembling an inverse-square law - then by diluting the drug to 1/250,000, the change rate might be around almost 21 seconds objective time to 1 second subjective. In other words, overkill in the other direction. There should be plenty of ways to handwave an in-between figure.
EnragedFilia
03:45:41 PM Sep 15th 2011
More importantly in my opinion, Mayuri is enough of a card carrying Mad Scientist to actually test his superspeed drug by administering huge overdoses to helpless captives, and thus may not be extrapolating at all.
http://tvtropes.org/pmwiki/remarks.php?trope=Main.WritersCannotDoMath