A fleet of 9 taxis must be dispatched to 3 airports: three to airport A, five to B and one to C. If the cabs are numbered 1 to 9, what is the probability that all odd-numbered cabs are sent to airport B?   What I have have come up with so far:   Probability the cabs are odd is $\frac59$ Probability they are sent to only airport B is $\frac13$ $\frac59 + \frac13 = \frac89$   Is this the right answer?
A fleet of nine taxis is dispatched to three airports, in such a way that three go to airport A, five go to airport B and one goes to airport C.  If exactly three taxis are in need of repair. What is the probability that every airport receives one of the taxis requiring repairs.  My method was total number of ways is (9!)/(3!*5!*1!)= 504 (this is correct)  Now you have three groups and of every group one position is already filled. So: ....R, ..R, R So the numbers of ways to distribute the rest is: (6!)/(2!*4!)=15  But according to answer model of my professor, it should be 90. So I assume he says the number of ways of distrubiting these 3 broken cabs over the 3 spots is 3*2*1. But to me this seems wrong? The broken taxis don't differ so R(1)R(2)R(3) is same as R(2)R(1)R(3). If you standing at the airport A, it doesn't matter which of the broken cabs stands there?
How to test for minimum amount of items in inventory and execute a command if true I am using the AmazingKit plugin on my Minecraft server to make inventory kits for players. In a command block I have the following command:  /tellraw @p ["",{"text":"Iron","clickEvent":{"action":"run_command","value":"_____"}},{"text":" / "},{"text":"Gold","clickEvent":{"action":"run_command","value":"_____"}}]   Which prints the following result: Iron / Gold.  When a player clicks on Iron, what command should I write where the empty space is _____ in order to check if the player has at least (>=) 20 iron ingots in his inventory and if he/she does, remove 20 iron ingots and execute /kit Basic. If the player has less than 20 iron ingots in inventory, the command won't be executed. Instead, Insufficient amount of iron ingots will be printed out.   Same applies when a player clicks on "Gold".  I'm on 1.14 version I am looking for an option to require a passcode to power off my iPhone. That way, if the phone is lost, the person who finds it cannot simply turn it off, rendering Find My iPhone useless. Is there a way to accomplish this? Does the 2020 Apple M1 MacBook Pro support 2x daisy chained Thunderbolt Displays? The Apple Silicon based  supports Thunderbolt version 3 and I'm wondering if anyone has tried connection one to an ? Of course you'd need to use one of Apple's Thunderbolt 3 to Thunderbolt 2 converters. I also understand that this version is limited to supporting only a single 4K or 6K display, but since the original Apple Thunderbolt Display is only 2K I’d want to try and daisy chain these. Can I run more than one external display from the Apple Silicon M1 CPU/GPU based MacBook Pro (or Air)? I'm trying to determine if 1317 and 116 can be written as the sum of three squares?  I have the condition that if it is not of the form $4^{\alpha}(8k+7)$ then it can be written as a sum of three squares, but how do I use this condition to work it out?  Thank you Quantum systems without a classical analogue? I am now reading the quantum mechanics textbook by Dirac (chap. 4, $\S21$, p. 88).   He says that his quantization procedure does not include all possible systems in quantum mechanics and there are systems without a classical analogue.  How is this possible? How to evaluate potential advisers on grounds other than their research/publications? While accepting an offer to grad school, one is basically entering into a lasting relationship with one's adviser - most likely, someone whom the applicant has never met before, and the only exposure has been through the potential adviser's website/publications. It is in the interest of both parties to ensure (to the greatest possible extent) that there are no personal/professional traits of either that hamper the formation of a pleasant working relationship - no-one would want to go through the ordeal of having to change advisers midway!  While the faculty has a chance to have a good look at the applicant's profile as well as his motivations (through his grades and SOP), the applicant doesn't have a similar opportunity. So, I'm interested to know what parameters can be used to gauge a potential fit. I've thought of the following:   Past students:  Did anyone ever drop out/change advisers midway, and if so, for what reasons? These would be a bit hard to find though, as I don't expect the faculty concerned would list them on their website. It would be great if anyone could let me know how to find out the list of incoming students to a department for any year. Publication rate, taking into account the venues where they were accepted. Time taken to graduate - though I accept this is more dependent on the student, a median figure should be telling ... What they did post Ph.D. - did anyone get tenure if they went into academia, or is almost everyone unable to break out of being a post-doc?  Tenure status: I'm a bit unsure about this, so wanted the community's opinions about it. Just so that I'm clear, I'm only trying to calibrate the applicant's expectations about the working style of his potential adviser - and hence need to know to what extent are the following "typical" assumptions valid.  Tenured professor  A full professor is more likely to get grant funding, hence less time spent on TAship - but could also mean less time/effort spent on interactions with students (either being busy with other projects/talks, or due to more commitments to family at that age).  Tenure-track faculty (Assistant profs)  More likely to be young and energetic, and could translate to more time spent on one-to-one discussions with grad students - but funding may prove to be an issue, and may have to be on TA for a longer period.   What other factors would be relevant in this matter, and to what extent am I correct/incorrect in either the factors considered, or for undertaking this exercise at all? Proof for triangle inequality for vectors Generally,the length of the sum of two vectors is not equal to the sum of their lengths. To see this consider the vectors $u$ and $v$ as shown below.  By considering $u$ and $v$ as two sides of a triangle, we can see that the lengths of the third side is $\| u + v \|$ and we have $\| u + v \| \leq \|u\| + \|v\|$.  Under what circumstance equality occurs and how can one prove that? Linear regression prediction interval So, say you are a wizard 15/warlock 2. You have the Lance of Lethargy invocation, which pushes an enemy you target with eldritch blast and hit back 10 feet. Say you put a demiplane entrance ~5 feet behind the enemy you target with it. When you hit, you throw the enemy in. Before all this, you had put a Glyph of Warding in there on one of the surfaces. What would be the limit to the trigger for this? Would it be forced to be touch or proximity, or could you base it off something like hostility towards the caster?      ... When you cast this spell, you inscribe a glyph that later unleashes a magical effect ... You decide what triggers the glyph when you cast the spell. For glyphs inscribed on a surface, the most typical triggers include touching or standing on the glyph, ... (PHB 245)   The key word here is "typical". Based on Google's definition, the informal definition of "typical" is     showing the characteristics expected of or popularly associated with a particular person, situation, or thing.   This means, if my assumption is true, that the triggers in the PHB are only the most common ones. Other than the one about being forcibly at maximum 10 feet in diameter in the PHB, I cannot see a limit. Though I probably should assume this would all be DM discretion, (and I know that I sound like a broken record here) but could the trigger be hostility toward the caster, or something else, like being a specific race, gender, from a specific place, etc., or would it be forced to being something from the PHB? New database server hardware and software inserts slower than old setup I would like to prove the following equality: $$k^{\phi(l)} + l^{\phi(k)} \equiv1\pmod{lk}$$if $\gcd(l,k)=1$. What methods can I use? Thank you for your help. PHP parse/syntax errors; and how to solve them Correct user names when tracking /etc/ in git repository and committing as root Is this an instance of Priori Incantatem? During the climax of Fantastic Beasts and Where to Find Them, Tina briefly duels with Graves and their wands appear to lock with each other (see picture). I believe this also happens some other times in the later Harry Potter films other than Harry and Voldemort's duel in the graveyard during Goblet of Fire.    We know that this is definitely a case of Priori Incantatem for the graveyard duel in Goblet of Fire, as the wands are locked for a sufficient amount of time for past spells to begin showing themselves (significantly, showing the people Voldemort had murdered), but is this the case for the other instances of wands locking? If so, does that mean there are a lot more wands out there with shared cores, as it was my understanding this could only happen if that criteria was satisfied? \documentclass[11pt]{article}  \begin{document}   The above equations on application of Laplace Transform become:  $$sL_1\hat{i}_{L1}(s) = D\cdot \hat{v}_{C1}(s) + D\cdot \hat{v}_{C2}(s) - D\prime \cdot \hat{v}_g(s) + (C_{C1} + V_{C2} - V_g + V_D)\cdot \hat{d}(s)$$ $$sL_2\hat{i}_{L2}(s) = -D\prime \cdot \hat{v}_{C1}(s) + D\cdot \hat{v}+{C2}(s) + D\prime \cdot \hat{v}_g(s) + (C_{C1} + V_{C2} - V_g + V_D)\cdot \hat{d}(s)$$ $$sC_1\hat{v}_{C1}(s) = -D\cdot \hat{i}_{L1}(s)+ D\prime \cdot \hat{i}_{L2}(s) + (-I_{L1} -I_{L2} - I_1)\cdot \hat{d}(s) -D\prime \cdot \hat{i}_l(s)$$ $$sC_1\hat{v}_{C1}(s) = D\prime \cdot \hat{i}_{L1}(s)- D\cdot \hat{i}_{L2}(s) + (-I_{L1} -I_{L2} - I_1)\cdot \hat{d}(s) -D\prime \cdot \hat{i}_l(s)$$ $$sL_l\hat{i}_l(s) = D\prime \cdot \hat{c}_{C1}(s) + D\prime \cot \hat{v}_{C2}(s) - D\prime \cdot \hat{v}_g(s) +(V_g - V_D - V_{C1} - V_{C2})\cdot \hat{d}(s) - R_l \cdot \hat{i}_l(s)$$  \end{document}   Error:   181 Underfull \hbox (badness 10000) in paragraph at lines 181--181 181 Overfull \hbox (22.63293pt too wide) detected at line 181 I have a list of structs and I want to change one element. For example :  MyList.Add(new MyStruct("john"); MyList.Add(new MyStruct("peter");   Now I want to change one element:  MyList[1].Name = "bob"   However, whenever I try and do this I get the following error:     Cannot modify the return value of   System.Collections.Generic.List.this[int]‘ because it is not   a variable   If I use a list of classes, the problem doesn't occur.  I guess the answer has to do with structs being a value type.  So, if I have a list of structs should I treat them as read-only? If I need to change elements in a list then I should use classes and not structs? Good books on "advanced" probabilities Why am I asked for a credit card number to download a free app? I  want to download free app in my iPod touch device and i have the following doubts.  Kindly resolve me doubts.   when i try to download it asks my credit card security number. since i am trying to download free app , why do i need to provide my credit card security code? Will i be debited for downloading the free app from app store?   I cant able to find any information regarding this on apple.  Please provide me some references about this from apple and please resolve my doubts.  Thanks a lot. How to delete all music on my iPhone Can more than one antibody bind the same antigen I'd like to clear something up about antibodies that I'm not sure I've understood in the articles I've read. Looking at concepts such as "affinity maturation", "monovalent antigens" and "polyvalent antigens" it seems as if there are multiple antibodies which can bind to the same antigen. (Although I think I'm right in saying that individual antibodies can only bind to one antigen?) However, when I read sentences like "It has been estimated that humans generate about 10 billion different antibodies, each capable of binding a distinct epitope of an antigen" on the Wikipedia page (for antibody) it does make it sound like it's one antibody per antigen? Is this the case? Or is it one antibody per epitope. Either way, to put this question in a nutshell:  Is it true to say that the same substance could bind with (and, therefore, be recognised by) more than one antibody, or not?  Also, if the answer is no, does that mean that antibodies with different binding affinities are classed as the same antibody or not?