Martin Sleziak's room

11:44 AM

I am not sure I agree. This question (the one related to "Mental Arithmetic. In the Public School of S. Rachinsky." can be answered by calculator, but I think that it was very well received and it is useful for the site. — Martin Sleziak 2 hours ago

Similarly, I do not see any problem with question of the type: "How do I calculate $26\times135$ by hand. Although in this case, I definitely prefer this question understood in a general way. (I.e., asking what is the algorithms to do this type of computations as opposed to asking what is the result specifically for the given numbers. But answers to question about specific numbers can also illustrate the general algorithm.) — Martin Sleziak 2 hours ago

@MartinSleziak Wasn't the point of that question to solve it without using a calculator? This makes it quite different, I think. I mean, I can ask a calculator to compute $\int_{-\infty}^\infty e^{-x^2} dx$, and it will spit out 1.772... or even $\sqrt\pi$ if it's sophisticated enough. That's not interesting, and if all you want is the numerical value, then math.SE isn't the right place. But the interesting part of the question is precisely how to do it without the calculator. — Najib Idrissi 2 hours ago

@MartinSleziak When the precise questions asked (omitting only the claimed "personal effort" context) are "$37\times29=?$" and "$15+16=?$" (the latter being "two huge numbers"), I'm more inclined to start looking underneath bridges. Furthermore, these specific questions will not have any value for future readers because who the hell is going to come here looking for those precise calculations and hoping to find general algorithms? — arjafi ♦ 2 hours ago

@NajibIdrissi That's basically what I wrote in my previous comment. I think that even things which can be computed by calculator or CAS, can be suitable questions for MSE. arjafi: The questions posted by the OP on the main might in fact be trolling (it is not easy to say). But since this question on meta and your answer are about this type of questions in general, the comment I gave was also intended to be about such question in general. — Martin Sleziak 56 mins ago

@MartinSleziak And in general I'll stand by this: if a question as phrased can be exactly answered by a basic four-function calculator, it doesn't belong on the site. The last thing we need is a glut of questions like "What is 42 ÷ 3?", "What is 285 – 262?", "What is 255 ÷ 17?", "What is 12 x 40?", "What is 17 x 97?", "What is 792 – 339?", "What is 658 + 478?", "What is 408 ÷ 24?", "What is 540 ÷ 27?", "What is 252 + 62?", "What is 919 – 603?", "What is 416 ÷ 32?", "What is 10 x 79?", "What is 989 – 537?", etc. — arjafi ♦ 5 mins ago

Reading your last comment, it seems that we more-or-less agree. In any case, we can continue this discussion in chat, if needed. So that we do not add too many comments here. — Martin Sleziak 7 secs ago

I think that our positions are not contradictory. (Especially considering the words "as phrased".)

The example in my first comment was this question:

139

Q: Mental Calculations

This is the famous picture "Mental Arithmetic. In the Public School of S. Rachinsky." by the Russian artist Nikolay Bogdanov-Belsky. The problem presented on a blackboard requires computing the following expression: $$ \dfrac{10^{2} + 11^{2} + 12^{2} + 13^{2} + 14^{2}}{365} $$ Using paper and ...

It asks about evaluation of $\frac{10^{2} + 11^{2} + 12^{2} + 13^{2} + 14^{2}}{365}$. In principle, this can be done by calculator. But the OP explicitly states, that they are interested in mental calculations.

Similarly the question suggest in my other comment, if I state it more carefully does not contradict your position: "How do I calculate $26\times135$ by hand? What is general algorithm for such computations?"

Personally I would not opposed even against the questions where the OP know to calculate something the usual way, but asks whether it can be calculated faster using something different. For example, a question directed to the "tricks" such as $48\times52=50^2-4^2$.

hardmath

1:25 PM

I'm concerned that moderator deletion of this Question:

math.stackexchange.com/questions/1792487/…

Martin Sleziak

@hardmath If it is indeed trolling, then the question would be deleted, anyway.

hardmath

was premature. Judging by the OP's efforts and the Comments by arjafi on the corresponding Meta.Math post, there is an entirely reasonable issue about how to perform multiple digit multiplication without using a calculator. Likely the Question should be edited to expose this issue better.

Martin Sleziak

Especially the first post by the OP sounded a lot like trolling: math.stackexchange.com/questions/1791370/…

"I tried to use my fingers and toes but I'm running out of them, can anyone help me?"

hardmath

I take your point. However I have in mind this Question: math.stackexchange.com/questions/15881/…

which ultimately I answered with a comparison of the usual long division and one that involves tabulating trial quotients by repeated addition.

Martin Sleziak

Your answer to that question seems interesting.

But certainly that question is quite different from the deleted one.

hardmath

1:38 PM

My point (narrowly drawn) is that the Moderator's dictum that four-function calculators are not necessarily a resolution of all "simple arithmetic" problems.

Martin Sleziak

I do not think that it is what arjafi claims there.

I suppose you agree with his comment that "What is 285 – 262?" would not constitute a good question.

Whereas I'd guess that this could be acceptable: "What is 285 – 262? What is a general algorithm for subtracting numbers with several digits?"

In any case, even if the question can be somehow improved to a reasonable (or even good/useful question), I would not go in that direction if the OP is simply trolling. That would just encourage the OP.

I am willing to give the OP benefit of the doubt that it is not trolling. But I am will not actively try to do anything in order to undelete the question.

So if you really think that this particular post should be undeleted, your options probably are: a) casting undelete vote; b) ask in Mod's Office; c) raise the issue on meta. But personally I do not think the question is not worth the effort.

I would agree with your comment, basically saying that a new question which is better formulated:

More especially the Question concerns how to multiply $37 \times 29$ by repeated addition. The "four addition problems" noted by @GerryMyerson got the OP as far as $37 \times 5$. To me it is reasonable to recast this Question as a problem about what more effective procedure will multiply integers of this "size". — hardmath 28 mins ago

To be honest, I am not entirely sure whether I should read the post on meta as a general question or the inquiry why the OP's question have been deleted. Maybe different reading of the question was partly the cause of the long exchange of comments between me and @arjafi.

hardmath

2:03 PM

Curiously we are not allowed to cast undelete votes on moderator-deleted posts. I am more inclined to raise my points here in chat in the hope that arjafi checks in.

And I don't want to feed the trolls!

Martin Sleziak

Ok. I did not know (or forgot) that mod-deleted post cannot be undeleted.

Since I posted a link to this chat room on meta, it is possible that arjafi (or some other moderator) will peek here and see what you wrote.

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$Mathematics$ Martin Sleziak's room