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''Murderous Maths'' is a series of books written by Kjartan Poskitt to make kids learn maths, and it might just have succeeded. The characters it uses include Riverboat Lil, the Evil Gollarks, [[MadScientist Professor Fiendish]], the gang of criminals led by Blade Bocelli... the list goes on, in the name of demonstrating various principles and equations. The books are filled with plenty of gags, as it is with many of Poskitt's books. Despite this, some fairly high-level maths (for kids' standards, anyway) is covered in a fairly lighthearted style.

The books in the series are:[[note]]The first two books in the series were originally part of ''The Knowledge'', a series of educational books covering different subjects, and hence covered many different fields of maths. It was decided that there was enough mileage to spin it off into its own range, and each subsequent book covers a specific area of maths[[/note]]
* ''Guaranteed to Bend your Brain''[[note]]Originally published as ''Murderous Maths''[[/note]]
* ''Guaranteed to Mash your Mind''[[note]]Originally published as ''More Murderous Maths''[[/note]]
* ''Awesome Arithmetricks''[[note]]Originally published as ''The Essential Arithmetricks''[[/note]] (basic functions, manipulating equations, long division etc.)
* ''The Mean and Vulgar Bits'' (fractions and averages)
* ''Desperate Measures'' (measurements and shape formulas)
* ''Do You Feel Lucky?'' (probability)
* ''Savage Shapes''[[note]]Originally published as ''Vicious Circles and Other Savage Shapes''[[/note]] (polygons and formulas for various parts of shapes)
* ''The Key to the Universe'' (number property equations, Fibonacci etc. right up to irrational transcendental numbers and imaginary numbers)
* ''The Phantom X'' (algebra and graphs)
* ''The Fiendish Angletron'' (trigonometry)
* ''The Perfect Sausage'' (formulas for just about everything, mostly shapes and physics)
* ''The 5ecret L1fe of [=Code5=]''[[note]]Originally published as ''Codes: How to Make Them and Break Them''[[/note]] (patterns and logic)
* ''Easy Questions, Evil Answers'' (formulas, problem solving, paradoxes etc.)
* ''The Murderous Maths of Everything'' (a bit of all of the above)

There are also several spin-off books, including a book of Su Doku and a follow-up book of Kakuro and other number puzzles, plus a puzzle book, ''Professor Fiendish's Book of Diabolical Brain-Benders''. Abridged versions of some of the books aimed at younger readers also exist.

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!!This series of books provides examples of:

* AccessoryWearingCartoonAnimal: Truffles wears only a scarf, glasses and occasionally a hat.
* AlienInvasion: The Gollarks try this several times, so they can tip over all the wastebaskets on Planet Earth. Gasp!
* AlliterativeTitle: The series name, as well as Awesome Arithmetricks and Savage Shapes.
* AlternateUniverse: Planet Mean in ''The Mean and Vulgar Bits'' looks exactly like Earth, but everything is the mean average. For instance, every family has 2.4 children, people have slightly less than ten fingers and ten toes, and they all die at the exact same age equivalent to the average life on Earth.
* AnachronismStew: The ''Su Doku'' book has a running story with Blade and the gangsters trying to complete one in a newspaper in [=1920s=] America. (Whilst the date is totally anachronistic, they are an American invention.)
* ArchEnemy: Professor Fiendish to the reader.
* {{Arrowgram}}: Princess Laplace sends one to Colonel Cancel and the Valiant Vector Warriors in ''Guaranteed to Bend Your Brain'' for help when she is imprisoned.
* ArtShift: Philip Reeve was unavailable for ''The 5ecret L1fe of [=Code5=]'' or ''The Murderous Maths of Everything'' (although he did return for ''Easy Questions, Evil Answers'', which was the GrandFinale as the final regular book in the series) because he was busy with the ''Literature/MortalEngines'' series. The replacement illustrators were very clearly trying to ape his style, to the point that the copyright notice gave him credit for the art being based on his work.
* AscendToAHigherPlaneOfExistence: [[spoiler:The titular machine in ''The Fiendish Angletron'' plots an unrestricted tan wave at 90 degrees to escape from its creator's money-making scheme.]]
* AuthorTract: ''Do You Feel Lucky?'' dedicates several pages to explaining why gambling is stupid and coming up with creative insults for people who use slot machines in particular, using the most TooDumbToLive character in the entire series, Binky Smallbrains, as an example.
* BackFromTheDead: Pythagoras. The reason why [[ItMakesSenseInContext is so he can stand trial and prove that his theorem works without using any calculations]] In ''Vicious Circles''.
* BigEater: Porky.
* {{BFG}}: You can rent them from the Murderous Maths' Weapons Department. These were used to explain how 'planes' worked by having a girl borrow a stereotypical laser gun [[ThereIsNoKillLikeOverkill to kill flies with]]. She starts off by being in the exact spot to kill two of them at the same time with the laser beam, but has difficulty trying to kill an additional third one, so she borrows another weapon which shoots out ''giant sheet panes of glass''. Then...
--> '''Girl:''' There's four flies now!
--> '''Weapons Department Clerk:''' ([[SerialEscalation brandishing a huge gun]]) Okay, they asked for it...
* BlatantBurglar: Three of the standard UK design appear together in ''Guaranteed to Bend Your Brain'', having stolen a large amount of money.
* BloodlessCarnage: The gangsters have attacked each other ''many'' times, yet somehow the only casualties come from among the ranks of Luigi's furniture.
* BreakoutCharacter: Professor Fiendish proved so popular that he eventually headlined his own puzzle book, as well as one of the regular books in the series, ''The Fiendish Angletron''.
* BuffySpeak: Dolly Snowlips claims to have a "hot cooking-machine what-d'ya-call-it job", which in English is known as an "oven".
* ComicallyMissingThePoint: In ''The Phantom X'', [[https://en.wikipedia.org/wiki/Diophantus#Biography Diophantus's epitath]] is presented as an algebraic puzzle. [[AbhorrentAdmirer Pongo [=McWhiffy=]]] thinks it means that if he wants to get married, he should grow a beard.
* CouldHaveAvoidedThisPlot: Professor Fiendish usually produces an overcomplicated scheme, but the most obvious is when he disguises as a technician and does building work for hours to install a fake Panic Button, which secretly summons him instead so he can give out a challenge. The reader points out to him that he could simply have turned up right away with the challenge, to which he has no reply.
* CutASliceTakeTheRest: In ''The Perfect Sausage'' a small piece of cake is cut for Porky so the area on top can be calculated. He then eats the remaining large part.
* DayInTheLife: Shown for a Pure Mathematician in ''The Key to the Universe''.
* DeathFromAbove: The Evil Gollarks randomly show up in ''Do You Feel Lucky?'' dropping extremely heavy objects out of their spaceship on people ForTheEvulz. [[TooDumbToLive This comes to an end when they throw the spaceship's control panel on someone.]]
* DecidedByOneVote: In ''The Key to the Universe'', a poll of 100 million people to determine if 1 is a prime number or not ends up this way... [[ParodiedTrope because over 99 million of the respondents answered "don't care" and several hundred more answered "don't know", meaning "yes" won by 8 votes to 7.]]
* DidntThinkThisThrough: Frequent with the Gollarks and Professor Fiendish.
** The Gollarks threaten to destroy the entire universe if a dice roll does not produce a four. Destroying the entire universe would include themselves... They decide the [[{{Pun}} die must die]].
* DisproportionateRetribution: At one point, the two barbarians, Urgum the Axeman and Grizelda the Grizzley, nearly end up killing each other over Grizelda's cat visiting Urgum's window box.
* TheDreaded: Gangsters who will cheerfully maul the hell out of each other given half a chance are terrified of Ma Butcher and Long Jake.
* EarlyInstallmentCharacterDesignDifference: Professor Fiendish's appearance didn't get nailed down until around ''Do You Feel Lucky?''
* EarlyInstallmentWeirdness: The first two books, having originally been part of another series, feature far fewer of any of the recurring characters and have no specific topic. Philip Reeve also didn't become the series' regular illustrator until ''Desperate Measures''.
** The story involving the gangsters in the first book (written with no expectation there'd be any more) ends in them all dying in a brawl at Luigi's diner. They pulled an UnexplainedRecovery in the second book, and later books {{retcon}}ned it to their brawls being a regular occurrence that just smash up all the furniture.
* ExactWords: To teach excluded angles, one of Blade's quests for money involves finding the coffin of fabled gangster Bluetooth Fonetti, who set up his own funeral to hide a stash of gold he stole in his coffin. Dolly begrudgingly gives them instructions on how to find it. They come up with a diagram which follows the instructions to the letter...except that after they left, Dolly knows they actually screwed up considering on how Bluetooth wrote the directions to his burial site. The book then draws a more-technical diagram which reveals why: There's ''two'' possible locations where the coffin is buried.
** Riverboat Lil asks Brett Shuffler if she can use her lucky die in a game. He agrees provided 'it's fair and has the numbers 1-6 on it'. It has those numbers, and also the numbers 7-12.
** The Pure Mathematicians laugh uncontrollably at a complex algebraic equation, saying they are laughing at nothing. The equation turns out to simplify down to equal 0.
* FriendlyEnemy: Grizelda and Urgum, usually. One book had her army and his seventeen sons fight each other in a friendly skirmish and have a party the following night comparing their new scars.
* FromBeyondTheFourthWall:
** When Wally the 1 moves around to different value positions in a number, the artist draws in 0s to help visualise.
** ''Desperate Measures'' advises you to cut a line across a page. A teacher is irritated by this suggestion, then on the subsequent page they are cut in half.
** Insects are squashed by closing ''The Mean and Vulgar Bits''.
* HarmlessVillain: Both Professor Fiendish and the Gollarks. The former always conducts a plan to either swindle you out of your money or just ForTheEvulz. The latter make continuous threats to destroy humanity, but they've failed so many times that it's pretty much become a RunningGag met with a DullSurprise.
* HellHolePrison: One is mentioned in ''More Murderous Maths''.
* HiddenDepths: As much as a dumbass Binky Smallbrains is, he has a penchant for fixing playing card hands without anyone noticing [[ItAmusedMe usually for jokes]].
* HousepetPig: Professor Fiendish's anthropomorphic pet pig, Truffles.
* HumanLadder: A giant one is created by the staff of Calamity Circus when they fall in a hole.
* InUniverseFactoidFailure: In ''Do You Feel Lucky?'', the Gabriellis attempt to get out of paying for their dinner bill by betting with the Bocciellis on a coin flip to see who pays, but flipped said coin beforehand due to one member claiming he's studied the laws of probability and thinks that you can fix the outcome by flipping a coin 9 times in advance (end result was 4 heads and 5 tails) since there's an equal chance for either side so they bet on heads, only for the Bocciellis to win with tails. The Gabriellis angrily find out from the narrator that they ended up reaching 4 heads and 5 tails by sheer ''[[{{Irony}} luck]]'' and coins don't have memory.
* LethalChef:
** Dolly Snowlips, as it turns out, cannot cook. Her first cake's smell overpowered her perfume and the gangsters just hid the slices.
** Pongo [=McWhiffy=] is the prime example of the series. He tends to cook generally unappetising burgers where one experimental line was so disgusting that an entire chapter in ''The Phantom X'' was dedicated to calculating trajectory based on how far and high his taste-testers threw them in disgust. Blue ketchup anyone?
* LettersToTheEditor: Parodied. Fictional letters are occasionally sent in from dissatisfied readers, then answered by the narrator.
* LittleGreenMen: The Gollarks fit this trope ''exactly''.
* LoopholeAbuse: In ''The Mean and Vulgar Bits'', the Boccelli brothers ask Luigi to cook a number of sausages, corn cobs and cannelloni rolls that will divide equally even if some guests don't arrive at their party. Luigi realizes he can cook ''zero'' food items, so no matter the number of people everyone gets nothing. He can close the restaurant for the week and have a holiday in Hawaii!
* MadMathematician: The cheerfully eccentric and overexcitable [[LovableNerd Pure Mathematicians]].
* MadScientist: Professor Fiendish.
* MeaningfulName: Pongo [=McWhiffy=]. Professor Fiendish. Rodney Bounder.
* MobileShrubbery: To avoid the barbarians, Hunjah the Headless disguises himself as a dung heap and wanders through a field to a shop.
* MonkeysOnATypewriter: {{Deconstructed}} in ''Do You Feel Lucky''. The theory is mathematically tested and 100,000 monkeys would between them write 'doyoufeellucky' once in 28 billion years - on a typewriter with only the 26 letter and 10 number keys.
* MuckMonster: The Crud creatures of Fastbuck, formed by mutated dumped radioactive and biological waste.
* MyHovercraftIsFullOfEels: The Gollarks ([[RunningGag yet again]]) attempt to destroy humanity by getting help from another alien race called the "Ploog Warriors". Problem is, they speak different languages, requiring an interpreter between them. All the Ploogs' translation attempts fail along with it taken up to eleven when the Gollarks enlist the help of several other species with individual languages which would require more interpreters between all of them than warriors. [[EpicFail This ultimately causes the entire plan to botch within a few minutes]] when they all can't understand the Gollarks' directions and crash into each other.
* NegatedMomentOfAwesome:
** In the gangsters' story in ''Desperate Measures'', Weasel (not entirely voluntary) is lowered out of a window on a rope as part of a heist, and plans to swing himself out and crash through the window of the room where a priceless painting is being held. For once in his otherwise miserable life he manages to win the respect of the other gangsters, and Blade is moved to tears by his bravery... except he ends up crashing through the wrong window, because the gangsters made the rope from their belts and braces and Weasel's weight stretched it out.
** ''Desperate Measures'' sees the Gollarks try to use a doomsday weapon to blow up the Earth in a chapter explaining scientific notation. The device is measured in zzaps, where each zzap is roughly equal to a giant volcano exploding. Unfortunately for the Gollarks, they set it to ''8.91 x 10^-14'', which leads to the weapon briefly shuddering before keeling over ineffectually since the output was a pitifully-tiny zzap.
** The chapter introducing algebraic equations in ''The Phantom X'' illustrations various examples with the barbarian leaders Urgum, Grizelda and Hunjah purchasing weaponry from the local superstore. It all adds up to a huge war about to break out... only for the chapter to finish before the big fight anyway. The barbarians are visibly displeased at not being able to try out their cannons and arrows.
* NearVillainVictory: At the end of ''The Fiendish Angletron'', [[spoiler:The Angletron has seemingly calculated the final shape's "finish line" length before the heroes, leading to Professor Fiendish proudly announcing the results before the reader has to buy his invention...only to discover that not only is the Angletron [[ItCanThink sentient]], it had no intention of being part of a GetRichQuickScheme and calculated an unrestricted Tan wave at 90 degrees just to escape to a different plane of existence. This leads to it finding freedom while Fiendish has nothing left to sell.]]
* NewspaperThinDisguise: The Boccellis and the Gabriannis hide themselves behind a giant newspaper as part of one of their criminal schemes.
* NintendoHard: ''Professor Fiendish's Book of Diabolical Brain-Benders'' is this for puzzle books. Exaggerated by the final puzzle, The Devil's Dice, which involves two dice with numbers such as 18 and 91 on them, so you can't tell whether it should be 18 or 81, 91 or 16, and so on; the challenge is to work out what the two numbers on the bottom of the dice add up to on the third throw, having been shown the results of two previous throws, and unlike every other puzzle in the book, ''no answer is provided''. (It was accidentally made UnintentionallyUnwinnable in early printings, which transposed the illustrations of the second and third throws.)
* NoFourthWall: The reader is frequently addressed by the narrator and some characters, and readers also appear in illustrations either to comment on something or to be involved in Professor Fiendish's schemes.
* OddballInTheSeries: ''The Murderous Maths of Everything'' is in full color with a larger book size, and returns to a similar style to the first two books, with no running topic and many past ideas revisited.
* OhCrap: The gangsters' reaction in ''Vicious Circles'', at the prospect of having to eat some of Dolly's cooking. Also their usual reaction whenever Ma Butcher and Long Silver Jake show up.
* PaperThinDisguise:
** One-Finger Jimmy attempts to disguise himself as a petrol pump using a bucket on his head and a hose in his mouth.
** Professor Fiendish with a false plastic nose and beard when he runs a shop in ''The Key to The Universe''.
* PaperTiger: The Gollarks sic a Battle Cruiser on humanity at one point. It's huge, looks ominous, packed with offensive weaponry, frequently referred to as TheDreaded, and can apparently move at a top speed of "180 glomps per mnult". So what went wrong? [[spoiler:It's revealed that a "glomph" is only a few kilometres and a "mnult" is 3 days. Turns out that it's ''slower than an average snail and tastes like lettuce'', [[SlowerThanASnail which it promptly gets outran by a horde of snails]] and eaten to scrap.]]
* ParodyName: Sheerluck Homes, a detective who struggles to solve cases, depending on pure chance or getting the crime wrong because he failed to consider all evidence.
* RageAgainstTheAuthor: Zig-zagged with Poskitt. He's either heavily worshipped (usually by the narrator) or dogged on by the Murderous Maths employees or the current book's artist.
* RunningGag: ''Key to the Universe'' has several judges giving "PUF" ([[FunWithAcronyms Pathetically-Useless Fact]]) awards to pointless maths facts throughout the book, culminating in the most top rated PUF being [[spoiler:"The number 'forty' is the only number in the English language to have its letters in alphabetical order"]].
** The number of calculators wrecked by performing impossible calculations is counted throughout ''The Fiendish Angletron''.
** In a chapter of ''The Perfect Sausage'', a semiperimeter is said to be useless for calculating the length of fence needed around a cow field as the cows can escape. One then shows up any time a formula involves the semiperimeter of a shape.
* SelfDeprecation: After the dangers of good jokes spreading are explained, the narrator says that the author goes to great lengths to make sure none of the jokes in the Murderous Maths books are at all funny.
* ShapedLikeItself: Chainsaw Charlie's chainsaw-shaped suitcase, as it turns out, contains a chainsaw-shaped chainsaw.
* ShoutOut:
** Professor Fiendish advertises his Fiendish Angletron with 'Get an Angletron - because you're worth it', referencing the L'Oréal advertising slogan.
** Some cows escape from a field because it has only half a fence. One remarks that they feel like [[Creator/SteveMcQueenActor Steve McQueen]] [[Film/TheGreatEscape on his motorbike]].
* SophisticatedAsHell: One gag has a Pure Mathematician give a very detailed and fancy-sounding description of a diagram. Turns out the diagram is shaped like a pair of underpants with each vertex spelling out "BIG PANTS".
* SpoofAesop: The Pure Mathematicians create a [[https://en.wikipedia.org/wiki/Sine_wave sine wave]] by driving a tow truck along a road and swinging a leaking paint can off the back. This actually works, but they are quickly noticed and chased by police. The moral of this is stated to be "Don't let a Pure Mathematician borrow your tow truck".
* {{Superhero}}: {{Parodied}} with Supersin, Cosgirl and Tandog. They have no superpowers but instead demonstrate trigonometry formulas, change into their costumes by sliding out of their house into a lake and have a [[BatSignal Supersin signal]]. [[spoiler:No surprises they're the Pure Mathematicians.]]
* SwitchingPOV: Mostly there is an omniscient narrator, but The Phantom X narrates in first-person some parts of that book and Professor Fiendish is the first-person narrator of the introduction to ''The Fiendish Angletron'' and much of ''Professor Fiendish's Book of Diabolical Brain-Benders'', with his pet pig Truffles taking over for the answers. Curiously, a few puzzles use the traditional narrative style.
* TakeAThirdOption: A variant on the "Dueling Wizards" puzzle in ''Do You Feel Lucky?'' has the three barbarians in a cannon brawl, but one is at a severe disadvantage compared to his other two opponents. His best option is to shoot ''away'' from both of them so Grizelda (with a higher chance of hitting her target) takes aim at Urghum since he has the best chance of hitting his target and thus is the most dangerous.
** In the same book, the narrator says when tossing a coin you can only win 50% of the time. The reader decides to call heads ''or'' tails, winning no matter the result.
* TakeThat: On occasion, the books have humorously poked fun at the ''Horrible Science'' series, including one experiment in ''The Phantom X'' involving woodlice and caterpillars being shredded into dollops, and has the passing remark: "When you've done a few Murderous Maths experiments, even the most horrible science will seem a bit dull". Somewhat justified in the introduction to ''The Key to the Universe'', as the author explains that while other subjects such as language, biology and history are interesting in their own right, they're not as universal between cultures compared to numbers.
* TheSecretOfLongPorkPies: Heavily implied in ''The Perfect Sausage'' when the Mayor of Fastbuck declares the butcher's sausages fail to conform to the titular shape. Suddenly he disappears and there is a new batch made...
* ThePigPen: Pongo [=McWhiffy=], whose defining trait is being perpetually surrounded by flies and well, fitted with a first name ''and'' a surname concerning bad smells.
%%* TooDumbToLive: Possibly the Evil Gollarks. Definitely Binky.
* TwoMenOneDress: [[spoiler:Two of the Pure Mathematicians]] in the Tandog costume.
* UpperClassTwit: Binky Smallbrains, one of several inhabitants of Fogsworth Manor. True to his name, he loses lots of money on a slot machine and gets scammed by his relative Rodney Bounder over a pair of oversized trousers.
* VagueAge: One of the puzzles in ''Professor Fiendish's Book of Diabolical Brain-Benders'' gives Primrose Poppet's (one of the residents of Fogsworth Manor) age as 13, but the way Philip Reeve illustrates her and some of her appearances (such as playing cards with the other Fogsworths) seem to suggest she is at least a little older.
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