Mathematics - 2011-01-16

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2:45 PM

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Q: Puzzler which I have a confident answer for, but doesn't match the multiple choice answers...

So, I've been forwarded a math problem with 5 possible answers, and I'm unable to get my answers to match any of the given answers... I'll not cloud the issue giving my working up front (but I will post it once I have some answers, for comparison). The question is this: And the possible answe...

anyone got any input on that? I'm pulling my hair out!

:(

@LessPop_MoreFizz Maybe they haven't played it yet

@Dave Let me have a look at it

Cheers mate - it's rather simple, and I usually breeze these kinds of questions, but I'm offically stumped!

To ze pen and paper!

@ArdaXi Lol! I've been through it already, but I'm convinced none of the answers match :(

I can't beleive the only tag I could use was 'fun-problem' :(

LessPop_MoreFizz

@badp the problems with that answer have nothing to do with it's factual information or lack thereof

2:50 PM

@Dave I was referring to myself :)

@ArdaXi Oh right :(

@badp Thanks for the input badp - can you see a flaw in my working (I updated the question)

@Dave You can't subtract percentages like that

I get 460,577

@badp oh my - it's 0.8% in total less, not 0.8 less than 12 :( - how embarassing :)

@ArdaXi Then answer, you've either got it right or you got it wrong in a way the professor foretell

3:01 PM

I did it the same way you did.

@ArdaXi Can you, perhaps, give me a brief work through?

425,600 × .12 = 51,072 × .992 = 50,663.424 ÷ .11

@ArdaXi 425,600 × .12 = 51,072 × .992 = 50,663.424 ÷ .11 = 460,576.58(18)

The only thing I did differently was instead of dividing by .11, I divided by 11 and did that times 100

how the hell did I get that number

Deletes comment in shame

3:03 PM

@badp Lol I just seen that disappear! Thanks folks, let me get my head around this all now! :)

@badp Anyway, I don't think hyphens are valid in XML tag names.

Yeah, your problem was subtracting percentages.

I thought I'd been cautious doing that too :(

You would have to subtract 0.8% from 11% to yield 10.992% for that to work.

Aahh, of course!

3:05 PM

I'll put that in an answer real quick.

Ideal!

@ArdaXi So the 50% of 15% is -35%?

@badp Unless it's applied to the same value.

← 34 messages moved from The Bridge

@badp If you first apply 15%, then 50%, it's 7.5%

3:11 PM

yes, so you can't just subtract percentages

If it is applied to the same value, you can subtract them.

This is about compound percentages.

(Notice how we're the only people in this room)

I think we're the only people in chat anyway

Fair enough.

I still can't believe my pitfall was subtracting percentages :(

It's okay :)

3:20 PM

Well, I'll head off just now - but thanks for the input :)

@Dave If your pitfall was the actual subtracting, I would be ashamed.

@ArdaXi Well, in my defense, I did the 12 - 0.8 just fine

I got 11.6 everytime.

Exactly, so it isn't -too- bad.

:-D

yeah, not the kind of mistake I'd make

If I had my Casio at hand I'd pet it now.

3:22 PM

I couldn't find mine :(

Enjoy - i.imgur.com/AaGqE.jpg

cya

user image

What did you have again?

user image

How cute.

The best non programmable non graphic calculator I could find, and I didn't look around too much.

Yeah, have fun not using that during exams.

Try the best programmable graphic calculator my school's money could buy

@badp Actually, this thing is standard fare on exams. You're pretty much screwed if you don't have it on you.

3:28 PM

@ArdaXi In Italy no exams I've been in allows programmables and many more don't allow graphicals.

Okay, these rules are rarely enforced, but they're there for the professor to screw you with if necessary.

Combine the steep price tag and barely anybody has one of those.

Math exams are impossible without these.

You need a graphic calculator to do them.

I guess we get simpler functions that are actually graphable by hand

with non-impossible-to-calculate limits and so on and so forth.

Yeah, we don't.

(You know, being able to graph functions by hand is part of the course.)

Applications of limits, derivatives, etc.

If they ask you something like "Give the maximum of <function>" you can use your calculator to approximate it.

If they say "Calculate exactly the maximum of" you need to do it algebraically.

3:31 PM

If they ask me "Approximate the maximum of function", I can approximate it by calculating its derivative, punching it in and then using the SOLVE button

but I've never been asked to.

The exam doesn't test our knowledge of calculators, yknow.

I've only just learnt to do derivatives.

@badp Our exams tests real-world applicable knowledge as well. Knowledge of calculators is much more useful in the real world. :)

@ArdaXi Real world? Who needs that.

@badp Er... you, apparently.

Although doing it all by hand made a lot of sense in the context of Software Engineering, provided that we will be writing the software for your calculators, in the real world.

But the software is already written! I think there is definitely something in Software Engineering courses about not re-inventing the wheel.

3:36 PM

@ArdaXi Sometimes the wheel is not licensed that way.

If so, you're not working for a big company, so you're probably not going to take off very well in this business

I doubt anyone in NL will buy anything other than Casio or TI

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