80%(30 + 40 / 4 x 5) =? Percent and PEMDAS - Practice BASIC Math!
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- Опубліковано 18 тра 2024
- Basic math practice - PEMDAS, order of operations, percent. Learn more math at TCMathAcademy.com/.
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I’m seventy. I was scared to death of math in school. I was in the D- Hall of Fame! I am grateful for you and how you explain things. Had you been my math teacher 60 years ago, I would have been a genius!!😀😀😀❤️
Do not be grateful for this video.
80%(80) is not valid mathematical notation. It's complete garbage. It doesn't mean anything. It's not how mathematics is written at all.
true for most people... and is where UA-cam is great because you can backup as much as you like/need.
Unfortunately what he's taught you here is rubbish. Not the calculations, but the notation.
80%(80) is not an alternative way of writing 0.8×80. It's not correct mathematical notation at all. It's meaningless gibberish. The % symbol is not used in this way in mathematical notation.
It's shocking that someone who purports to be a teacher doesn't know this.
@@gavindeane3670 "80%" in this case is being used as a "verbal" expression. You're quibbling over "terms". 80% does equal 0.8 of something. Yes he should have stated,, "What is 80% of (30+40/4x5)"Well done...but it's not evil...is that what you're suggesting? Or is it just "first half of the 21st Century anal retention and I can't find a house to rent"?
@@ceeemm1901 That's exactly the point. "80%" is something you would write if you were presenting this as a word problem in English, like "What is 80% of 80?".
But he hasn't presented it as a word problem. He's presented it as if it's an expression written in mathematical notation. Only what he's written is not correct mathematical notation at all.
Muddling the two forms of presentation like that is really sloppy and incompetent from anyone who purports to be a teacher. But it's arguably even worse for this guy to be writing such nonsense because his target audience is very likely to include people who won't know any better. You couldn't blame them at all for seeing the question, watching his video, and then thinking that this is correct, normal notation.
got it 64 PEMDAS with a twist thanks for the fun
It's not a twist. He's made up his own personal form of nonsense that isn't mathematical notation at all.
@@gavindeane3670 Did your probing not turn out the way the aliens promised?
Yep, got me with the parentheses. I took it as (30+40)/(4x5).....so, no parentheses, it's open PEMDAS slather! Hahaha......great, I really learned something with this one, cheers.I'm 67 and am digging your vids big time!
Interesting problem structure. Thanks to PEMDAS got 64 working it in my 85 year old head.
It's a completely gibberish problem structure. It's not correct mathematical notation at all.
@@gavindeane3670 So what's your math YT channel then, scammer?
@@ceeemm1901 Why would you think I've got a UA-cam channel?
I was not good at math in school, but at my age, I love it. Thanks for explaining it. It is easy for me to work it out correctly 👍🏿 🙂
I say 40/4 = 10 then multiply by 5 = 50 then add 30 +50 = 80 then multiply by .80 thus 64!
That's exactly what I did
be honest if this wasn't a multiple choice question you wouldn't have solved it correctly, or it would not have been as easy to solve.
Where were you when the “Good Sisters “ were beating Math into me! Hated Math until I started watching your videos! You’ve opened my mind to understanding Math!
Yes, been away from Math for 60+ years. With a bit of practice on TabletClass site, especially review of PEMDAS, the Math seems to still be in the old brain somehow.
Thanks, we here look forward to more.
when writing computer code I ALWAYS used profuse parentheses as debugging code is complicated enough without adding in uncertainties from mixing "+," "-," "×," and "÷." Such confusion wasn't needed.
When I write code, I find it more confusing when trying to do everything possible in one line of code. I'd much rather be "less efficient" using six lines of code as opposed to "less readable" doing the same thing with one line.
I tire quickly OF PEMDAS stuff...
written correctly the problem is
80%(30 + ((40/4)×(5)))
that is not any more correct than the way shown in the video
@@adrianm.2043the original problem was:
80%(30 + 40/4 × 5)
which is different than
80%(30 + ((40/4)×5)))
because it ia clear that everything inside parentheses is done first.)
alternately
(30 + 40/4 × 5)
leads to confusion requiring PEMDAS
That is exactly as wrong as the expression in the video.
Written correctly the question would be
0.8(30+40/4×5)
Or if you want to write parentheses where the precedence rules imply them, then it's
0.8(30+((40/4)×5))
@@gavindeane3670 do you enjoy confusing people??
@@tomtke7351 Has something confused you?
I want to say it again:
when writing equations in computer code be sure to use parentheses profusely... and make sure to count both open-parens ans close-parens to make sure they are equal. Learned this at blurry 3a.m. when debugging code. AGAIN -- using parentheses at 3a.m. is easier than PEMDAS.
Stop writing code at 3AM!
I've waited Fifty years to learn that.. Extreeme thanks.
OneLove 💚
The answer could be either 64 or 24 based on how it's written. Just depends if you take the / to mean ÷ or the slash to mean a fraction bar where it would be 40 over 4x5
This. Try entering the equation into one of the many online calculators. A "/" results in the denominator being 20 and the result is 25.6. " ÷ " returns 64.
/ is the correct symbol for division in mathematical notation. ÷ is deprecated and should not be used.
There's no basis for giving multiplication higher precedence than division like you've suggested. 30+40/4×5 unambiguously evaluates to 80. I get that it's open to misinterpretation if you don't know the grammar rules - that's why he's teaching the grammar rules.
The bigger question is why are you complaining about that when he's written "80%(" at the start? "80%(" is not mathematical notation at all. It's nonsense. It's complete gibberish.
@@markfujimoto3530
Which online calculators are you using?
I've tried Google, WolframAlpha, MathPapa, Microsoft Math Solver, Mathway, 7 calculators in various apps, and my actual hardware scientific calculator. They all say 40/4×5 is 50. Which is completely unsurprising.
The / and ÷ symbols don't mean different things (other than ÷ being deprecated). Most calculators just choose one or the other symbol for division. However, Google, WolframAlpha and MathPapa allow you to enter either symbol, and whether you enter the expression as 40/4×5 or 40÷4×5 the answer is still 50.
The operator makes no difference. Go left to right one number at a time.
The "/" should never EVER be interpreted as a "fraction bar."
64
We follow BODMAS bracket order division multiplication addition subtraction
I got it thanks to you, a week ago
I would've got it wrong for sure.
61 here, got 64. ready for rocket science class now...
Does the left-right sequence for multiplication and division also apply to addition and subtraction?
Yes.
D. 64
Got the correct answer, but only because I've been watching a lot of your videos. Upvoted!
Please save your upvotes for when he actually teaches mathematics.
What he's written here is not correct mathematical notation at all, and he really should know better.
@@gavindeane3670 Please provide a detailed explanation as to why the provided notation is not correct, what would be the correct notation, and why.
Thanks!
D
64.
Do the brackets first.
Division and multiplication go left to right, so do 40/4 to get 10. 10x5=50, so we now have 30+50 which is 80.
Now we find 80% of 80. 80/5=16
80-16=64
64. No acronym needed. Kind of crazy that basic mathematics escapes more and more people by the day
I guess I am going to have to go with 64 by the answer options given.. but I would have done this problem differently. I looked at the problem on the right as one thing over another thing, and tried to solve for both parts before dividing the denominator into the numerator.. so I went 30+40 and got 70 and then multiplied 4x5 and got 20.. and divided that 20 into the 70, and then multiplied that answer by .80 which got me 2.8... but that answer was not in your list, so I simply did all MDAS in order regardless of how I viewed the problem.. and that got me 40/4 which is 10 and then multiplied that by 5 which give me 50, then added 30 which gave me 80 and then multiplied that by .80 which gave me 64.. which is one of the answers in your list, so I am going with that..
Solved in my head, no pencil/paper/calculator needed, the answer is d) 64.
Using PEMDAS, the parenthetical part evaluates to 80, so 80% of 80 = 4/5 * 80 = 64.
...okay, let's do the actual math:
0) 0.8 ( 30 + 40 / 4 * 5 ) -- start
1) 0.8 ( 30 + 10 * 5 ) -- do the Division inside the Parentheses since it's the first MD left to right
2) 0.8 ( 30 + 50 ) -- do the Multiplication inside the Parentheses
3) 0.8 ( 80 ) -- do the addition inside the parentheses
4) 64 -- final answer, since 80% = 4/5, 1/5 of 80 is 16, so 80 - 16 = 64.
As long as you remember PEMDAS then done in seconds 🙂
You have to memorize PE MD AS
DM SA
You need to remember PEMDAS and you also need to be able to tolerate the nonsense "80%(" notation at the start. That is not a valid way of writing "0.8×(" at all.
@@gavindeane3670 When was the last time you went to a party? A real one, of course, with women in attendance, not just a sausage fest of frustrated mathletes and their pocket protectors. Were you the life thereof?
Let's do the brackets ..
30 + 40 / 4 x 5 divide first
30 + 10 x 5 multiply next
30 + 50 add next
80 and now it's 80% of 80 80/100 x 80
64
This is the first one I messed up, because when we have PEMDAS we still go left to right, which was my mistake. But then I figured out 40/4 = 10. 10x5 is 50. Plus 30 is 80. 80% of 80 is 64.
it is easier to calculate if you only reduce the % fraction to 8/10 than 4/5.
d) 64; 4/5*80=4*16=64
I say 40/4 = 10 then multiply by 5 = 50 then add 30 +50 = 80 then multiply by .80 thus 64!
Why isn't 40/4 x 5 not 40/20? I see your way, but it makes more sense to me to see the last part as a fraction with 40 as the numerator and 4 x 5 as the denominator.
Because the / division operator is not a grouping symbol. It can't be - there's no way for it to indicate how much or how little of what precedes or follows it should be grouped.
If you want that grouping effect you need to use something that is a grouping symbol, i.e. parentheses.
40/(4×5) is 40/20
.8([200/4] +30)
.8(80)
64
I did it that way too.
Deu 64, letra D.
D.64.
Got in trouble in the second grade because I was doing fourth grade math
I solved this in my head in 64 tenths of a second.
Easypeasy again: 4/5 x 80 = 4 x 80/5 = 4 x 16 = 64
PEMDAS is misleading. It should be PE(M or D)(A or S)
d)64
D....64
Here's an example of poor construction. In order to avoid any confusion, 40/4 should be written (40/4). Without them it would be quite possible to come up with the answer of 40 otherwise.
Excel gives the answer of 64 with or without parentheses, but I would put them in anyway, especially if using Excel for repetitive calculations using variable quantities.
That's your example of poor construction here?
At least 30+40/4×5 is correct and meaningful notation, even if there is scope for misinterpretation.
On the other hand "80%(" is just nonsense. That's not a valid way of writing "0.8×(". It's not correct or meaningful mathematical notation at all.
@@gavindeane3670 how is the thing that has "scope for misinterpretation" correct meanwhile saying 80% is meaningless?
Why? How else could 80% be interpreted. Everybody knows that means 0.8. Calculators have a percent symbol as well. Theres nothing wrong with using 80% because theres no way to misinterpret it; meanwhile, theres a perfectly clear way to misinterpret 40/4×5
@@tripleg2513 Some calculators have a % button. Many do not. "Percent" is not a mathematical operation and the button is not needed.
30+40/4×5 is correct mathematical notation with a precise, unambiguous meaning, albeit you do need to understand the grammar of mathematical notation in order to interpret it correctly.
"80%(" is not mathematical notation. The % sign might be used if you were presenting a mathematical word problem in English, like "what is 80% of 80?" but it is not used in mathematical expressions.
The closest it comes to being used in mathematical notation is in computing, where % is commonly used as the modulo operator (i.e. calculating the remainder after doing a division). In that usage 80%(30+40/4×5) = 0 because when you divide 80 by 80 there is no remainder. But that's obviously not what's going on here.
The fact that you guessed correctly what the author meant here is besude the point. He claims to be a teacher, and he is specifically making content for people who are not very good or not very confident with mathematics.
It is trivially easy to write this question using correct mathematical notation:
80
------ (30+40/4×5)
100
That's what he should have done, particularly given the fact that his target audience is likely to include people who wouldn't know any better. If he writes like this, why on earth would it occur to them to think that it might not be correct?
Ambiguous notation. / historically is a fraction bar.
If you want to think of it as a fraction bar, fine - it's forty fourths. This fraction is then multiplied by 5.
@@jamesharmon4994 WRONG! If the "/" is a "fraction" bar, then left of the bar is the numerator which is 4 and to the right of the bar is the denominator which is the "product" of 4 X 5. One should NEVER arbitrarily split a product. As written it implies that the 4 X 5 is the denominator. If such is NOT the case it should be made clear by enclosing the 40/4 in parenthesis. As @jamesharmon4994 said. "Ambiguous Notation"
@@AFmedic WRONG! If that was a fraction bar, the denominator is simply 4. If the denominator was 4x5, it would have to be written (4x5)
24
Yet another episode of “let’s eat grandpa.”
d)
80%(30+(40/4)×5)) =64
80%=8/10×80/1=640/10=64.
my mistake seeing 4 x 5 as if they had a parenthesis.
Sixty four
A bunch of subtraction in my head gave me 64
I got 64
The answer is 64
So it is NOT Pemdas.. it s pedmas.. without paranthesis it could go both ways...
PEDMAS is PEMDAS. They're the same thing.
So PEMDAS is PEMDAS, until it isn't.
.80x80= 64
19 minutes to explain a 1 minute problem
The answer is 64%
He's trying to ask "what is 80% of 80?". The notation he's used isn't correct but that's the question. So the answer is 64, not 64%.
his guy is too long winded how many frigen times must he exspalin PEMDAS
Only 69 my answer D 64
W long can we drag out and try to dumb down a simple explanation; andvturn it into an exercise in exasperation. Hmmm? Well how long was this 50k'th explanation of PEMDAS? Apparently thats how long it takes.... Wow
Don't watch then and don't be rude. People watch these for many reasons, I for one watch them to see how the math is explained to a young child, I want to see more of the meticulous explanations.
Could use less talk and get to the point. I started watching this while waiting for the Southeastern Line to Stratford international. It was still playing when I walked into the Westfield mall. Fook sake, mate, get on wit it.
If you are that good, why do you watch?
Fail. Because undefined through lack of clarity.
You know nothing about Pemdas. Did you realize that there is no subtraction in your pemdas.
All are wrong.
The whole question is wrong. "80%(" isn't mathematical notation. It doesn't mean anything.
Stop leading people down the primrose path of PEMDAS or PEDMAS or BODMAS or whatever BS acronyms you want to use. Teach them to write unambiguous succinct expressions instead. Real mathematicians would never write the pap you publish nor would they teach such useless lessons.
It is important that people are taught the basic grammar of mathematical notation (although the stupid acronyms are unnecessary and unhelpful - they can get in the bin).
But it's surprising that that's what you chose to.pick up on here. Did you not see "80%(" at the start? That is complete nonsense. It's meaningless gibberish. It's not mathematical notation at all.
This problem is ambiguous only to the illiterate.
@@jamesharmon4994It's not just ambiguous, it's complete nonsense.
But that's not because of the 30+40/4×5 bit. That bit is fine. The problem is before that. "80%(" is not mathematical notation. It's not a valid way of writing "0.8×(" at all. It's just gibberish.
@@gavindeane3670 In your opinion.
You need to stop teaching math wrongfully, as you are misleading many people with a simple operation. I will cite 4 points of proof, as I have in your previous videos that you are wholly wrong, while noting that between you and me, you aren't the one who had taken all of the required math courses for a PhD at Duke and Michigan State, and who taught math at two universities, and at one of the top 10 private secondary schools in the US (at least at the time), Cranbrook, which currently has a tuition of $40,000 per year.
From the following points of proof that I share, either I, along with every math PhD I studied under at two universities is wrong, along with every math PhD whose textbooks I studied and taught out of, or you.....making money on UA-cam by screwing up 4th grade math.
The error you continue to make is with division, with a product in the denominator. Let's just work with 40/4x5, as that is your error.
1) Note, there are no parenthesis, so what is the numerator? Clearly 40. What is the denominator, clearly 4x5, which by definition is a product, of two values multiplied by each other.
So 40/4x5=40/20, which is 2. But that isn't what you do, as you wrongfully assume parenthesis, treating this expression as (40/4) x5, which violates the definition of an implied multiplication operator, as you can't assume parenthesis.
2) You are saying.....no, there can't be a product in the denominator of a fraction without parenthesis, which is wrong. Are you telling me that you can't have 4x5 in the denominator, which again by definition is a product, without writing it as (4x5)? That is wrong, as yes, you can have products in the denominator of two numbers multiplying each other, as basically everybody knows.
3) You violate the definition of the vinculum, which is the dividing line, and for which values are grouped above the line, and below the line So, with 40/4x5, what is above the line? Only 40, that is it, that is the denominator. What values by this definition are below the line...4x5, which is a product.
But that isn't what you have done, as you have violated the definition of the vinculum by grouping one value in that product, which is 5, above the line. Again, you are assuming parenthesis in violation of an implied multiplication operator where they don't exist, and treating this expression as (40/4)x5.....but it isn't written that way.
What you are doing is saying that 5 is grouped above the line, but the expression also wasn't written as 40x5/4, but that is how you are treating it.
4) There is a simple algebraic proof, that a/bc=a/bx1/c, and not (a/b)c, with the exception of maybe all variables equaling 1, or a equaling 0.
Stop teaching math wrongfully and screwing up whomever believes your videos. For these people there is a great video made by a math tutor entitled PEMDAS is a lie, for which she cited the calculations that engineers make.
What happens is that terrible instructors such as yourself, screw up the kids in pre-algebra, which is then corrected in algebra.
Shame on you, as you have seen my comments proving you wrong by definitions of implied multiplication operators, the vinculum, of having a product in the denominator without parenthesis, and by a simple algebraic proof, and yet you keep putting out videos to misinform people and screw them up.
Just terrible, as teachers are supposed to acknowledge facts, admit their errors, and teach properly, for which your grade on that is an "F".
You're posting this nonsense again. Please stop. You do not understand the words you are using.
Moreover, why on earth are you criticising the 3/40/4×5 part when the expression starts with "80%(". Do you not realise that "80%(" is complete nonsense? It's not mathematical notation at all.
Your criticism is not just incorrect, it's aimed at completely the wrong part of the notation.
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