And how do you arrive at the answer

And how do you arrive at the answer
50: I eliminate the 7+ 7 at either ends, which leaves 49+1 (7*7+7/7)
Algebraic Expressions, Order of Operations/P.E.M.D.A.S. I
Think 7+(7*7)+(7/7)7 = 7 + 49 + 1  7 = 57  7 = 50
7 + 7 * 7 + 7 / 7  7 Multiplication and division always happen first if there are no parentheses.
7 + (7*7) + (7/7)  7
7 + 49 + 1  7 Addition and subtraction read lefttoright.
56 + 1  7
57  7
50
since it has been shown that you are a troll and crank i just want to say that this is a 'problem' that any 13 year old could do, where algebra is taught. order of operands is one of first things learned. this may confuse people on social websites but not science people.
your english is worse than mine. hard to believe. please reread. i said 'it has been shown that you are a troll ...' i was just pointing out your lack of maths. i am not caring much what you think of me. your opinions do not matter.
i will give you a little math problem. rearrange this problem using reverse polish notation so it is not ambiguous any more
[QUOTE=MagiMaster;548133]@Mayflow, Try Wikipedia.[QUOTE]
I don't see how that sort of convolution relates to the subject. It was a very simple math thing. I do, however appreciate niceness, which few here have offered. I knew the answer before I asked the question, and it is very simple math.
since i know you will not or can not convert this problem to RPN and you will not try to learn here is the answer:
7 7 * 7 7 / + 7 + 7 
this is only one solution. there are others.
For part b, it could be that he sometimes let's frustration get the better of him ( as we all do at times), the exchange here was a direct result of some very childish trolling by the OP in another thread (this is why they are currently suspended). Carrying over arguments from thread to thread is not good but we've all done it...
a) maybe you learned a little more than the OP. my friends tell me that algebra is first taught in seventh grade here in usa. the OP is seventh grade maths. RPN is slightly more advanced. did you already know RPN ? these types of maths 'problems' in the OP are common on social sites like facebook. first one i have seen on a science forum. but that is ok too because i think there are children here who can learn from this. or adults trying to improve maths skills.
b) that i was overzealous in pursuing a known troll. a troll that was suspended. i admit i should not have come to this thread in my zeal. but please take a few moments to read the post by this troll in other threads. here is a good one for starting: Ok, brainiacs, and all, any thoughts on this? but still, i should not have come to this thread. i am sorry for doing that. but i am not sorry for my treatment of this troll.
No worries, been there and done it myself. Some people are so ignorant they wind you up so much you lose perspective.
Probably the most elegant formula. Process of elimination is always a good troubleshooting technique.
Now, how about this one? What does 9x7i>3(3x7u) =? (I tossed in the parenthesis stuff on this one) :)
Ps if you know internet slang, do NOT interpret the answer too personally literally!!
Right answer, you think therefore you are....
Here is one I do not know the answer for:
Is ego sum, ut pinor equal to or less than or maybe the reciprocal of Cogito ergo sum?
Although that question falls beyond the scope of the Mathematics subforum, I will give a brief answer:
I see no (logical) connection between those statements. The former is not related to the latter statement (which has its own shortcomings, cf. post #18).
I can do ANOVA, TTests, ZTests, Quadratic formulations etc... But if you asked my to do long division (Which IIRC is like 4th grade math) it would probably take me 30 minutes just to recall the steps/procedure involved or to solve it in a way that takes many unnecessary steps.
What could I possibly gain by fibbing about not remembering how to do long division? I am telling the truth, and hope you'll just take my word for it. The fact is I haven't had to apply those skills since elementary school  and I've never had to divide 1564 apples amongst 32 friends either.
*I haven't ridden a bike in many years either  I'd probably suck at that too now.
Hey, how do you determine a square root by hand?
No, it's not your English  which is quite good if it isn't your primary language. I'm just terrible at distinguishing between serious comments and jokes on the internet. The lack of tone and social cues makes it almost impossible for me to understand when something is meant as a joke.
I am not seeing anyone telling me how to figure out a square root of a number by hand yet.
you really do not want to read or learn something on your own. do you ? if you did an interent search like i suggested you would find dozens of sites. here is one.
Calculate square root without a calculator
I can do it by guess already. That did not help to do it by formula.
you read the first sentence of that site. go down a few paragraphs. do you want someone to read it to you now ?
that algorithm will give you sqaure roots to decimal places. try guessing that.Finding square roots using an algorithm
There is also an algorithm that resembles the long division algorithm, and was taught in schools in days before calculators. See the example below to learn it. While learning this algorithm may not be necessary in today's world with calculators, working out some examples can be used as an exercise in basic operations for middle school students, and studying the logic behind it can be a good thinking exercise for high school students.
and there are dozens of other web sites with this algorithm. . maybe you need a video. try youtube
Ok, I guess guessing at it and narrowing it down is as good as it gets. That is all that algorithm does.
that algorithm will give as many deciaml places as you want.
you do understand that scientists and engineers had to do these tasks before there were even mechanical calculators. slide rules were used after about 1600.
there are several other algorithms easily found with internet search
Last edited by Chucknorium; April 5th, 2014 at 08:02 PM.
Good old 40^2 hummm? You do realize that good old me can do this by hand as well. Well actually that one I just could figure in my head. Doing squares is easy, the square roots are not as easy.
something something .45 something something.
Last edited by Chucknorium; April 5th, 2014 at 08:53 PM.
Reply to original question: Here is a mnemonic to remember in which order to perform calculations:
BODMAS: Brackets Off*, Divide, Multiply, Add, Subtract.
* in other words perform all the operations inside any brackets
So in your question:
there are no brackets.
next perform the division 7/7 = 1
next perform the multiplication 7*7 = 49
so now you have 7+49+17
next do the additions 7+49+1=57, so now you have 577
finally the subtraction 577=50
OB
Last edited by One beer; April 9th, 2014 at 02:24 PM.
I find you harsh. Determining square roots with a slide rule (as I did at school and university) is the same doing them with log tables. But if you do not have either of these, then doing really "by hand" needs some form of iterative procedure. This is far from trivial and a perfectly reasonable question for Mayflow to ask.
The Wiki answer attached shows what a pain it is:Methods of computing square roots  Wikipedia, the free encyclopedia
I would not blame anyone for finding these pages of hieroglyphics intimidating.
Is that why the Egyptians used the wheel? It always yielded a predictable distance, based on Pi
If you mean square roots, all I know is to fumble around until I can close in on them, or use my beloved Excel.
Even the Babylonians could do better than "fumble around":
See exchemsist's link for details.The basic idea is that if x is an overestimate to the square root of a nonnegative real number S then \scriptstyle S/x\, will be an underestimate and so the average of these two numbers may reasonably be expected to provide a better approximation
I say "even" but obviously they developed pretty advanced maths (and gave us 60 minutes, 360 degrees, etc) because calendars were really important to them (because of geography).
I saw the link. Exchemist is a helpful poster!, but it is still stumbling around. I just make a guess and square it, and then go higher or lower as needed.
The point of the better iterative methods is to have a more accurate idea of how much to go higher or lower. (And minimise the number of iterations to get to a desired level of accuracy.)
I am not a mathematician, ('BODMAS' was given to me by my maths teacher many years ago), but I am 99% certain that you treat the root symbol like brackets too, in other words perform all operations written under the root symbol's horizontal line before finding the root of the result. Then continue with BODMAS.
Yes, you can write a root expression as √(blahblahblah), so I'm sure that's a good way to look at it.
Ah, BODMAS take me back…..to a dusty classroom, high above a side street in South Kensington in the mid 60s, with a geriatric teacher in a brown suit and a terrible pipe smoker's cough. My 10yr old son learnt BDMAS last year (they've dropped the "O" as being unnecessary and confusing, evidently. I was taught it meant "Of", as in 1/5th "of" 20 = 4).
56
What you do..
1; Start excel
2; ctrl + c (7+7*7+7/77)
3; enter (=) in any cell
4; ctrl + v (7+7*7+7/77)
5; press enter
6; solution is 50
Don't calculate by yourself, just know how to get to the answer.
Be a manager, the less you know how to do, the more people you know who can do things, the better you seem to be, without doing anything. I feel there is a meaningfull quote in here somewhere.
Is it easier if it is posted as 7+(7*7)+(7/7)7?
You can cast aside the 7 and 7 as they equal 0.
Now you have (7*7)+(7/7)
which reduces to 49+1 which equals 50.
The order of procedure was not outlined without the parenthesis, but it still needs to be followed for the correct answer. If you put it as originally stated and punch it into a calculator you will get 56, which incidentally is closer than a lot of answers I got by some relatively intelligent people like 1, 7, and most disappointing, by a friend who knows math a lot better than I do, 49.
Order of Operations  BODMAS
Sometimes 11 year olds are going to outdo older people because of better teaching or parenting and because certain things are just fresher in the mind for them. Just saying Bodmas may not be a good teaching process without explaining what Bodmas are though.
Now, if your 11 year old understands 1/2 spin better than I do,  (he probably can't understand it less than I do.) Or photons. Those guys baffle me. This is all good, a lot to enjoy learning.
No one is just saying BODMAS: the explanation has been given higher up in this thread.
What is mildly unexpected, to me at least, is that there are contributors to this forum who can't do this correctly. Could it be a modern dependence on calculators, do you think, or is it that we just have some members who, while expressing an interest in natural science, are nonetheless poor at basic arithmetic?
It depends on the calculator; some correctly handle operators and some don't. And, of course, some use Reverse Polish Notation ...
There seems to have been a spate of posts on LinkedIn recently, where people post trivial arithmetic problems like this with headlines like "99% get this wrong" (usually followed by 99% getting it right). Very annoying.closer than a lot of answers I got by some relatively intelligent people
I don't find BODMAS a particularly useful mnemonic as it isn't a real word. I have to work out what the mnemonic was supposed to be from the precedence rules...Order of Operations  BODMAS
miscalculations sorry
I understand the theory behind long division. But quite honestly I suck at arithmetic anymore. Computers and calculators have ruined me. I doubt I could get the correct answer doing long division by hand nowadays  even though I have a degree in math, and I graduated with 4.0 even! Of course, I don't use that math in my day job, so it hardly counts much anymore
I have this same problem...
A month or two ago as part of my preparation for starting a teacher training course I did a week of being a teaching assistant in a primary school (9/10 year olds), and helped most with the maths. From my admittedly limited experience, long division now seems to be taught almost exclusively by something called the "chunking method". I'd never heard of this and had to pick it up on the fly to avoid the kids thinking I was an idiot. Basically if you are trying to divide a number by say 15, the kids write in the corner the "chunks" of 1 x 15 = 15; 2 x 15 = 30; 5 x 15 =75 and 10 x 15 = 150. They then subtract the largest possible "chunk" from the number to be divided and repeat until you can go no further and make note of the remainder (if any). Then they go back and add up the chunks they have subtracted to get the answer. Is this how it is taught elsewhere nowadays?
Interesting, because that is not how my son was taught it (he is just turning 11). He has been taught the old way, more or less as I recall doing it myself. But he is at an independent school preparing for Common Entrance, which I imagine may be more traditional than the state system is.
The school I ws helping at was an independent (but not fee paying) church school. I don't know if the standard state schools do it differently...
I was also taught the traditional long division algorithm, but for doing division in my head I "naturally" just assumed the "chunking" method. It also works well for multiplication, considering that multiplication and division are inverse operations. And also keeping in mind the Fundamental Theorem of Arithmatic.
Of course I never told any teacher ever what I was doing in my head.
Rewarding memorization and ignoring synthesis, no wonder America is educationally a shithole.
Careful!You seem to be channelling RomanK hereAmerica is educationally a shithole
That would be because a stopped clock is still right twice a day.
I'm not saying that a good proper education is unavailable in America, but a shitty one is readily available; South Carolina Christian School Fourth Grade Science Quiz
I honestly have no idea what they teach anymore. I've just been volunteered to help a friend's daughter, who has been having a hard time with long division. Her dad just "knows" the answers for each step in long division, and can't explain it to her, and she's getting very frustrated. So I'll explain how I do it, which is apparently much more similar to the chunking method you described, although I always thought of it more like bootstrap estimation.
Consider 435 divided by 25. Obviously 25 can't go into 4, so we'll start with the 43  the first bit bigger than 25. But we can ignore the 3 for now, and just start with the 40, it'll make it easier. And realistically, we can round 25 up to 30 as well. So what we're talking about for our first pass is how many times can 30 go into 40? Only once, of course. So you write down 1 over the 3, and you multiply 25 times 1 and write the answer under 43 and subtract to get 18.
Now this usually works, but sometimes it doesn't  that's part of the deal when you're estimating. If your remainder in that first step is larger than 25, then you just have to increase your multiplier and do it again. So next step: You drop the next number to make your numerator larger than your denominator, and you're looking at 185 divided by 25. Only we're going to round again and call it 180 divided by 30... so we'll guesstimate 6. Now it just so happens this gives you 150, which leaves a remainder of 35, which is bigger than 25, so you have to up it by one. Bump it to 7 and do over  now you get 175 and a remainder of 10.
Then it's a matter of whether you're doing remainders or fractions or decimals... Same process applies though. Just round to a reasonable level, make a decent starting guess, and run with it. It works well enough without having to somehow magically know that 25 goes into 185 seven times... because I just don't carry that in my head. It's not how my brain works.
7+7*7+7/77
= 7+49+7/77
= 7+49+17
= 56+17
= 577
= 50
Any objections?
I was taught long division the "traditional" way but the way I do it in on the fly is to divide numerator and denominator by a common factor until I get to something "sensible" that I can work out in my head.
My main problem with math is trying to get over the feeling that I'm dumb by doing it slow.
I know if I don't do it slow I'll screw up cause eventually I wont be able to read my own handwritting correctly
That's the thing isn't it  whether you remember it? Doesn't really matter whether it's a mnemonic or whatever, as long as it can be easily remembered.
Silly Old Hens Can't Always Have Twins On Asking: SOHCAHTOA. This again was from my maths teacher, (hello Miss Cook).
I daresay I could come up with a slightly more 'hip' mnemonic, but hers still works for me.
My class was taught H=Hypotenuse, B=Beside and O=Opposite (~ P in post #88).
The mnemonic was "Old Human Beings Have Old Bones", with Sin, Cos, Tan just assumed (remembered) as the order.
But in my head I mostly just remembered that with Sin and Cos it was one of the smaller sides divided by the hypotenuse (otherwise you'd not get a number less than 1) and Sin was "Ugly" and Cos was "Nice". Somehow with the angle A being calculated at the intersection of H and B made it more "balanced", whereas with Sin using the opposite side, it seemed disjointed.
I beg to differ,
It is very valuable to have a rough idea of the approximate answer as you are calculating the actual answer. This was the key to using a slide rule, you knew roughly what the answer was going to be, which enabled you to correctly place the decimal point, and guarded against gross errors.
What has speed got to do with anything? Likewise use of fingers? Honestly, I have a degree in math, I'm good at math. But I'm very slow at arithmetic, and I'm slow at algebra or I make errors. And if I'm doing arithmetic mentally, I use my fingers! I was never particularly good at memorizing stuff  I am much better and understanding concepts. So I understand how addition, subtraction, multiplication, and division work. I grok the concepts. What else is necessary, really? Why should I have to memorize and be able to regurgitate addition at the drop of a hat, when I can simply memorize a few key points, and know how to get to where I need to be form there?
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