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muriel_volestrangler

(106,238 posts)

140. A counter-example to your interpretation comes from the Feynman lectures

Sat Aug 10, 2019, 09:16 AM

Aug 2019

With this interpretation 1 ÷ 2x is equal to (1 ÷ 2)x. However, in some of the academic literature, multiplication denoted by juxtaposition (also known as implied multiplication) is interpreted as having higher precedence than division, so that 1 ÷ 2x equals 1 ÷ (2x), not (1 ÷ 2)x.

For example, the manuscript submission instructions for the Physical Review journals state that multiplication is of higher precedence than division with a slash, and this is also the convention observed in prominent physics textbooks such as the Course of Theoretical Physics by Landau and Lifshitz and the Feynman Lectures on Physics.

https://en.wikipedia.org/wiki/Order_of_operations#Mixed_division_and_multiplication

See http://www.feynmanlectures.caltech.edu/I_06.html - it is written in one line as "within the deviation 1/2√N", and the full formula right after that is clear that it is

1
____
2√N

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8/2(2+2) what do you come up with? [View all] kimbutgar Aug 2019 OP

16. nt Atticus Aug 2019 #1

+1 indeed 16 is the correct answer nt mr_lebowski Aug 2019 #2

uh huh.. Maxheader Aug 2019 #155

Not following you ... I said 16 is the correct answer ... mr_lebowski Aug 2019 #158

It was my understanding that there would be no math TeamPooka Aug 2019 #92

hahahaha. n/t OneGrassRoot Aug 2019 #120

You win the internet today KentuckyWoman Aug 2019 #131

I was right the other day my SO brought this up from FB... Anon-C Aug 2019 #3

Nothing, 16 is absolutely the correct answer ... someone else is missing something ;) mr_lebowski Aug 2019 #4

16 Dr. Strange Aug 2019 #5

Ok I'm a substitute teacher who is learning common core kimbutgar Aug 2019 #6

That is silly. Drahthaardogs Aug 2019 #8

4x1/4 is 1 kimbutgar Aug 2019 #20

Correct, but it is not the same problem. n/t Ms. Toad Aug 2019 #23

Yeah. But that has nothing to do with the equation in question. GulfCoast66 Aug 2019 #34

wut? jcgoldie Aug 2019 #10

I would appreciate a link to an explanation of that method missingthebigdog Aug 2019 #24

Seconded! FiveGoodMen Aug 2019 #98

As someone with two math degrees - Ms. Toad Aug 2019 #37

If that is what they are teaching children those children are going to be seriously math challenged. honest.abe Aug 2019 #60

It is 8 divided by 2, not 2 divided by 8 LeftInTX Aug 2019 #152

Please Excuse My Dear Aunt Sally jcgoldie Aug 2019 #7

That's right! customerserviceguy Aug 2019 #28

1 SlogginThroughIt Aug 2019 #9

Pemdas SlogginThroughIt Aug 2019 #11

No jcgoldie Aug 2019 #12

oh really? SlogginThroughIt Aug 2019 #15

I promise jcgoldie Aug 2019 #18

Yeah, same with addition and subtraction. Dr. Strange Aug 2019 #30

Yup. (Former math teacher) Ms. Toad Aug 2019 #22

Perhaps more accurately (PE(MD)(AS)) mr_lebowski Aug 2019 #35

A hole in your argument. KY_EnviroGuy Aug 2019 #137

Exactly. tinrobot Aug 2019 #16

You only do 4 passes, not 6 Ms. Toad Aug 2019 #19

That was a great explanation! jcgoldie Aug 2019 #26

Shaking 30 year old cobwebs out of my math teaching brain . . . Ms. Toad Aug 2019 #39

I came up with 16. Polly Hennessey Aug 2019 #13

No one who knows anything about calculations would write a formula like that because they'd Hoyt Aug 2019 #14

My point exactly wryter2000 Aug 2019 #80

Yup... SidDithers Aug 2019 #86

In the old days we used Reverse Polish Notation and we liked it. hunter Aug 2019 #133

My initial solution was 16 based on what I know it's 16 kimbutgar Aug 2019 #17

I mastered the equation from an former Nazi rocket fuel scientist while I was in the Army Brother Buzz Aug 2019 #25

Here is how you get to 1: missingthebigdog Aug 2019 #21

1 applegrove Aug 2019 #27

1 Turbineguy Aug 2019 #29

This was covered in the above discussion jcgoldie Aug 2019 #33

Goodness. I learned this in 8th grade! GulfCoast66 Aug 2019 #31

1. Nt BootinUp Aug 2019 #32

It's actually 16 my good friend ... mr_lebowski Aug 2019 #36

Weed relaxed error, that's my story, lol. BootinUp Aug 2019 #42

I get stoned as I pray ... check this one out brother ... from last year ... mr_lebowski Aug 2019 #44

You got good taste in music jcgoldie Aug 2019 #91

I like fishwax's answer, #45 best. hunter Aug 2019 #48

Fake math. The answer is what i say it is. dem4decades Aug 2019 #38

Ah yes! Mossfern Aug 2019 #84

Well, you're the president Clash City Rocker Aug 2019 #101

My high school algebra teacher got fired the year after I was in her class. 3catwoman3 Aug 2019 #40

6.693 x 10 to the power 25 sarisataka Aug 2019 #41

I come up with .... rufus dog Aug 2019 #43

fraction bars function the same as brackets/parens, which is how people are getting the answer 1 fishwax Aug 2019 #45

It occurred to me that people are taking the / to refer to a fraction bar jcgoldie Aug 2019 #49

You're right about the keyboard, but the same principle applies w/ an elementary division symbol fishwax Aug 2019 #68

Arbitrary jcgoldie Aug 2019 #75

I agree with you, though do appreciate the exposition by fishwax mr_lebowski Aug 2019 #82

Yes I agree jcgoldie Aug 2019 #89

yeah, looking back I wound up being more confusing than I intended with my initial post fishwax Aug 2019 #122

but it is arbitrary, as your own final few sentences show fishwax Aug 2019 #93

Just to cherry pick one sentence... jcgoldie Aug 2019 #97

that's cool about the calculators fishwax Aug 2019 #100

No; putting it into my scientific calculator, using in place of / muriel_volestrangler Aug 2019 #134

That's exactly what I did to get 1. The bar is a division bar, and Nay Aug 2019 #153

The good old fraction bar! LeftInTX Aug 2019 #150

Shunting-yard algorithm? hunter Aug 2019 #46

A big yawn! struggle4progress Aug 2019 #47

1 treestar Aug 2019 #50

Did'nt we haves this test a few weeks back? Hotler Aug 2019 #51

166.6666% Incorrect blugbox Aug 2019 #64

8/2(2+2) 8/2(4) 8/8 1 Afromania Aug 2019 #52

multiplication and division have the same precedence so go left to right... Joe941 Aug 2019 #102

It's newer notation LeftInTX Aug 2019 #159

88 FBaggins Aug 2019 #53

Lounge??? Nt USALiberal Aug 2019 #54

Typed into MS Excel Trumpocalypse Aug 2019 #55

People rember PEMDAS, but forget the rest of the rules of operation. Hotler Aug 2019 #56

Calm down everybody kimbutgar Aug 2019 #57

Its a math problem jcgoldie Aug 2019 #66

8/2 means 8 divided by 2. Ms. Toad Aug 2019 #72

It's 16. Getting to 1 is possible but not accurate. Claritie Pixie Aug 2019 #58

An equation should never be written that way. honest.abe Aug 2019 #59

we should ALL demand non-ambiguous math!!! not_the_one Aug 2019 #69

(8/2) is redundant. Ms. Toad Aug 2019 #70

A necessary minor redundancy to eliminate confusion like we see in this thread. honest.abe Aug 2019 #73

I'm a programmer, as well, Ms. Toad Aug 2019 #104

I suppose you could get away with it.. honest.abe Aug 2019 #105

Any programmer Ms. Toad Aug 2019 #106

Well we certainly see things differently. honest.abe Aug 2019 #110

We do. Ms. Toad Aug 2019 #112

So those confused by this arbitrary math rule have less than 7th grade math skills?? honest.abe Aug 2019 #113

You seem to be confusing the level at which math skills are taught Ms. Toad Aug 2019 #116

FWIW, if you enter the equation into Google search it formats the equation exactly I wrote it. honest.abe Aug 2019 #123

It's still redundant, Ms. Toad Aug 2019 #124

I think the Google search engineers and I are more correct. honest.abe Aug 2019 #125

I had a degree in math from 1978 and I wrote programs as part of that degree LeftInTX Aug 2019 #162

Considerably different computing power in those days. Ms. Toad Aug 2019 #163

It's a grotesque thing. hunter Aug 2019 #108

True. n/t Ms. Toad Aug 2019 #109

Exactly. The point of writing equations (or anything) is to make the meaning clear to the reader. DanTex Aug 2019 #94

1 Proud Liberal Dem Aug 2019 #61

... jcgoldie Aug 2019 #63

16. jmg257 Aug 2019 #62

One FakeNoose Aug 2019 #65

I hope the original problem looked more like this: Rstrstx Aug 2019 #67

1 nini Aug 2019 #71

You Tube explains it: both are, or were, correct jimmy the one Aug 2019 #74

The Distributive Property gives me 1 LeftInTX Aug 2019 #156

This is boring. There are rules of sequence which are arbitrary. Who cares if you don't know it? Cicada Aug 2019 #76

A billion C_U_L8R Aug 2019 #77

Don't be fragile Midnightwalk Aug 2019 #78

How it's written is misleading wryter2000 Aug 2019 #79

White and gold. If you think it's blue and black, you're wrong. JustABozoOnThisBus Aug 2019 #81

My guess was 1 Tommy_Carcetti Aug 2019 #83

If it's ambiguous, then it's not a good mathematical question... SidDithers Aug 2019 #85

Eight halves is 4 Mossfern Aug 2019 #87

Ah shit pwb Aug 2019 #88

42. Douglas Adams said it, I believe it, and that settles it. Buns_of_Fire Aug 2019 #90

Parentheses first which is 4 ismnotwasm Aug 2019 #95

A poorly written mathematical expression. DanTex Aug 2019 #96

Reminds me of this classical Chinese poem 2020Junker Aug 2019 #99

yeah the problem with this is... Takket Aug 2019 #103

It's an ambiguous question, and depends on leftmost or rightmost binding rules Recursion Aug 2019 #107

Mr Cash would be proud. lpbk2713 Aug 2019 #111

PEMDAS tells me it's 16. DangerousRhythm Aug 2019 #114

Technically it could be either as multiplication and division are equal. NutmegYankee Aug 2019 #129

1 mfcorey1 Aug 2019 #115

Potatoe. LuckyCharms Aug 2019 #117

Tomatoe MadLinguist Aug 2019 #127

1 GeorgeGist Aug 2019 #118

This Is an exercise in ambiguity Silver Swan Aug 2019 #119

At least it got us off politics ! kimbutgar Aug 2019 #121

16 wendyb-NC Aug 2019 #126

8 divided by 2 multiplied by 4 equals 16 aikoaiko Aug 2019 #128

In the 50's they taught me 16 KentuckyWoman Aug 2019 #130

16 denbot Aug 2019 #132

What is the following: muriel_volestrangler Aug 2019 #135

20,000. KY_EnviroGuy Aug 2019 #138

One KY_EnviroGuy Aug 2019 #136

No that would be Trumpocalypse Aug 2019 #139

A counter-example to your interpretation comes from the Feynman lectures muriel_volestrangler Aug 2019 #140

Type it into excel Trumpocalypse Aug 2019 #141

Hmm, what do I consider more authoritative, Richard Feynman, or Excel? muriel_volestrangler Aug 2019 #142

Excel. Trumpocalypse Aug 2019 #143

Nobel. muriel_volestrangler Aug 2019 #145

No Excel it the standard Trumpocalypse Aug 2019 #147

As punchlines go, that's an unexpected one, but pretty funny (nt) muriel_volestrangler Aug 2019 #148

Except writing it with a fraction bar as you did... jcgoldie Aug 2019 #144

No, implicit multiplication is conventional muriel_volestrangler Aug 2019 #146

You hit the nail on the head. Conventions have changed..... KY_EnviroGuy Aug 2019 #149

So in modern math what is LeftInTX Aug 2019 #161

Interesting. honest.abe Aug 2019 #164

1 5X Aug 2019 #151

1 Throck Aug 2019 #154

I shall go for a beer. Throck Aug 2019 #160

Poorly written equation zipplewrath Aug 2019 #157