Illuminati-R-Us

tubeswell wrote:I think I remember some math convention learned many moons ago in my now hazy youth, whereupon if there isn't a function symbol, you should multiply. But this has become somewhat arcane knowledge for me.

Well, 10x, (20)17, 30(15), and (96)(14+2) would also suggest multiplication to me. However, with numbers only, you need some operator or other punctuation - you can't write 5 times 2 as 52, for reasons that should be obvious.

Also worth noting, there could be 30+ years between what was taught to you all and myself. Might play some part in difference of educational methods.

Dragon Star wrote:Also worth noting, there could be 30+ years between what was taught to you all and myself. Might play some part in difference of educational methods.

Hmmm, now that is an interesting observation.

It sounded rather simple to me. Lance asked, "how does this add up?", so I added it up.

Arneb wrote:It sounded rather simple to me. Lance asked, "how does this add up?", so I added it up.

Mee too.

I guess my title could have been misleading. The real question is: Is there any way this is something other than an addition problem?

Lance wrote:Another one is: 20 + 30 * 0 + 1 = ?
A: 51
B: 21
C: 1
D: 0

Of course the only right answer is B: 21, but it is often the least chosen.

I get 50, by adding before I multiply. I'm not sure why I did that, presumably mis-remembering rules from forty years ago, or by using the invisible brackets.

This is where PEMDAS comes in. You do the 30 * 0 first, as if it were in parenthesis.

Lance wrote:This is where PEMDAS comes in. You do the 30 * 0 first, as if it were in parenthesis.

That acronym bothers me, and the Wikipedia page has some issues with it as well. Specifically, addition and subtraction are of equal precedence, as are multiplication and division. The acronym could easily be misinterpreted to mean that multiplication comes before division, and addition comes before subtraction.

Does anyone remember the old HP calculators, with RPN, so you didn't need parentheses/brackets? If everyone used PN or RPN, there would be no need for any rules on order of operations.

Мастер wrote:Does anyone remember the old HP calculators, with RPN, so you didn't need parentheses/brackets? If everyone used PN or RPN, there would be no need for any rules on order of operations.

I have no knowledge of this at all. Must ... Go ... Learn

I agree that the acronyms leave a bit to be desired. I wonder if there's a better way.

ETA: I vaguely remember running into PN or RPN ages ago. I think I remember it as being bizarre and confusing, but only due to lack of actually using it for any length of time.

Мастер wrote:

Lance wrote:This is where PEMDAS comes in. You do the 30 * 0 first, as if it were in parenthesis.

That acronym bothers me, and the Wikipedia page has some issues with it as well. Specifically, addition and subtraction are of equal precedence, as are multiplication and division. The acronym could easily be misinterpreted to mean that multiplication comes before division, and addition comes before subtraction.

Does anyone remember the old HP calculators, with RPN, so you didn't need parentheses/brackets? If everyone used PN or RPN, there would be no need for any rules on order of operations.

Wouldn't that lead to human sacrifice, dogs and cats living together and mass hysteria?

Lianachan wrote:Wouldn't that lead to human sacrifice, dogs and cats living together and mass hysteria?

Only with infix notation.

Lance wrote:ETA: I vaguely remember running into PN or RPN ages ago. I think I remember it as being bizarre and confusing, but only due to lack of actually using it for any length of time.

RPN == Reverse Polish Notation

Essentially, each time you put in a number, throw it onto the stack. Each time you put in a binary operation, apply it to the two numbers on the top of the stack, and replace them with the result of the operation.

So if you want to do 7+(19*3), it is like this:

1) Input "7" - stack = {7}

2) Input "19" - stack = {7 19}

3) Input "3" - stack = {7 19 3}

4) Input "*" - stack = {7 57}

5) Input "+" - stack = 64

If what you mean instead was (7+19)*3, then:

1) Input "7" - stack = {7}

2) Input "19" - stack = {7 19}

3) Input "+" - stack = {26}

4) Input "3" - stack = {26 3}

5) Input "*" - stack = {78}

Both achieved without parentheses brackets.

Polish Notation means the operations go first, rather than last. So the first one would be

+ 7 * 19 3

and the second would be

* + 7 19 3

I think if you are not used to it, it is probably very difficult.

I remember writing some machine language code back in the early 80s and the numerical operations were done like this. But in machine language, pretty much everything was done like this.

Lance wrote:

tubeswell wrote:

Dragon Star wrote:...
If my Algebra 2 teach wrote this and said "solve":

54
22
__

I can guarantee not everyone would use addition, .....

I think I remember some math convention learned many moons ago in my now hazy youth, whereupon if there isn't a function symbol, you should multiply. But this has become somewhat arcane knowledge for me.

Yup. So the answer to Dragon's equation is 1,188. It's nothing implied or assumed, it's just following the rules. That's why there ARE rules; so you don't have to guess.

I feel like I need to clarify my comment here. I'm not trying to suggest Dragon's example is proper or okay, just that it is solvable because there are rules.

Lance wrote:This is where PEMDAS comes in. You do the 30 * 0 first, as if it were in parenthesis.

I thought I must be misremembering something. I used to be good at maths since it is logical and there are rules, I could often work out what we were about to be taught by what was on the board and then sit and have what I had already worked out explained to me. Of course like any language if you don't use it for nearly forty years you forget it.

I learned several times the rules for what to do before what when facing a string of numbers with signs between them. I never remember. it always seemed to me, and still does, that any expression that is presented like that is poorly presented. And a set of parens makes abundantly clear what you want. Between my college degree, and my career in technical services, it is drummed into me that it is paramount to eliminate ambiguity, eliminate ways for people to misinterpret, keep them from fucking up.