Need help w/ math

[watts16]

Ok this chapter we are using vertex form to solve story problems.

Here is the Prob

A square, which is 5cm by 5cm, is cut from each corner of a rectangular piece of cardboard snd the sides are folded up to make a box. If the bottom of the box must have a perimiter of 50cm, what would be the length, width and height for the maximum volume?

Thanks please help i need to see all the steps

thanks

Greg

[partyboy300ex]

what kind of math are you in?

[watts16]

college track algebra

[wilkin250r]

First off, if a 5cm square is cut from each corner, and the sides are folded up, then height is automatically going to be 5cm, right?

Tell me you grasp this, and we'll move on.

[watts16]

yes

[wilkin250r]

Volume is L*W*H.

If height is fixed at 5cm, then volume becomes L*W*5.

So, maximum volume will occur when L*W is at it's highest value. THIS is where your vertex form comes in.

If the perimeter of the bottom of the box must be 50cm, that means 2L + 2W=50. Solve for either one, it doesn't matter. Let's do L.

So, L=25-W.

Now, plug that into your first formula, L*W*5 then becomes (25-W)*W*5=volume.

[watts16]

ok thanks

[wilkin250r]

In quadratic form, this becomes (-5W^2)+125W=volume. Put this into Vertex form and find the max.

Now, unfortunately, this is where I leave, for three reasons.

1. I'm not going to do the whole thing for you.

2. I want to go home.

3. I have NO idea how to put that quadratic into Vertex form, it has been way too long since I've done those transformations.


However, I CAN tell you that the max occurs when W=L. If you get some other answer, you did it wrong. ;)

[watts16]

yeah i just needeed to get it into quad form then i know how to do the rest

[400exrules]

wilkin do u know anything about radicals? Im a junior in algebra 2, and its kickin my azzz. Ive always done good at math my whole life, but this year im doing terrible, its like the teacher is speakin a diff. language. He goes way to fast for me. I failed the first 9 weeks (half a semester) with a 67, 3 points from getting a D and passing. Its the first time ive ever had an F at the end of a grading period.

[Quad18star]

Originally posted by wilkin250r
In quadratic form, this becomes (-5W^2)+125W=volume. Put this into Vertex form and find the max.

Now, unfortunately, this is where I leave, for three reasons.

1. I'm not going to do the whole thing for you.

2. I want to go home.

3. I have NO idea how to put that quadratic into Vertex form, it has been way too long since I've done those transformations.


However, I CAN tell you that the max occurs when W=L. If you get some other answer, you did it wrong. ;)

Have you ever taken an IQ test ?? One little guy on my shoulder is pushing me to ask you what your IQ is ... the other one is saying " No don't ask ....your IQ is way below his ... he'll just make you look like a dummy" . You pretty much got the answer to most any question .

[JKWGA400EX]

ok what did u say wilkin?lol thats like jiberish to me.



i hate that stuff.






jared

[wilkin250r]

Originally posted by Quad18star
Have you ever taken an IQ test ?? One little guy on my shoulder is pushing me to ask you what your IQ is ... the other one is saying " No don't ask ....your IQ is way below his ... he'll just make you look like a dummy" . You pretty much got the answer to most any question .

I've never taken an official, sanctioned IQ test, administered by a certified psychologist. But I have taken several unofficial ones. You know the type, online and such.

Depending upon the particular test, I have scored anywhere between 145 and 170, usually around the 155 mark. I generally get lower scores with the "quick" tests, under 20 minutes, and score higher on the more lengthy, involved tests.

Aren't you glad you asked? ;)

[wilkin250r]

Originally posted by 400exrules
wilkin do u know anything about radicals? Im a junior in algebra 2, and its kickin my azzz. Ive always done good at math my whole life, but this year im doing terrible, its like the teacher is speakin a diff. language. He goes way to fast for me. I failed the first 9 weeks (half a semester) with a 67, 3 points from getting a D and passing. Its the first time ive ever had an F at the end of a grading period.

If it's math, I can help you. However, I don't know each and every method and all the different terminology, so help me out.

What do you mean when you say "radicals"? Give me an example.

I took algebra 1 in 6th grade, 2 in 7th, geometry in 8th, now trig in 9th. It sucks.

[wilkin250r]

Originally posted by 400exrules
wilkin do u know anything about radicals?

Ok, by radicals, you mean roots. Like square roots, cube roots, and so forth.

Yeah, old hat. Whatcha having problems with?

[punker69q]

Originally posted by Quad18star
Have you ever taken an IQ test ?? One little guy on my shoulder is pushing me to ask you what your IQ is ... the other one is saying " No don't ask ....your IQ is way below his ... he'll just make you look like a dummy" . You pretty much got the answer to most any question .


This math question is pretty simple for any kind of engineer. If you could see the kind of math we have to go thru in engineering, you would understand why wilkin always got the answer to those questions!

To have an idea, simple read any book about differential equations or some advance statistics or calculus.

[400exrules]

Originally posted by wilkin250r
Ok, by radicals, you mean roots. Like square roots, cube roots, and so forth.

Yeah, old hat. Whatcha having problems with?

like, simplyfying radicals with fraction exponents.

here's a practice quiz from the chapter/section of my book to show you what im talking about

i have a quiz on it monday and i dont understand a lick of it. My teacher is horrible at teaching, everyones failing his class.

k this whole chapters hard for me, but this is the hardest.

http://www.glencoe.com/sec/math/studytools/cgi-bin/msgQuiz.php4?isbn=0-07-827999-2&chapter=5&lesson=7&headerFile=10&state=tn

thats chapter 5 lesson 7, here's lesson 6:

http://www.glencoe.com/sec/math/studytools/cgi-bin/msgQuiz.php4?isbn=0-07-827999-2&chapter=5&lesson=6&headerFile=10&state=tn

[wilkin250r]

Ok, there is some stuff in there that is absolutely NOT correct. It can't be.

I saw one question that asked you to simplify the square root of 1285, divided by the square root of 1610.

If you use a calculator and actually figure the answer, it's about 0.893. It's CERTAINLY less than 1, since the bottom number is larger than the top number.

However, all the options they give are all OVER 1. None of them can possibly be the right solution.

The only thing I can think is that I'm missing a font or somehow not displaying properly. I must be missing something, because it doesn't make any sense.

[popo]

The math teacher always wanted to argue with me, saying pie are square.

Not Uh! Pie are round, some times shaped like a taco pending from your vantage point.

[bwamos]

Originally posted by wilkin250r
Ok, there is some stuff in there that is absolutely NOT correct. It can't be.

I saw one question that asked you to simplify the square root of 1285, divided by the square root of 1610.

If you use a calculator and actually figure the answer, it's about 0.893. It's CERTAINLY less than 1, since the bottom number is larger than the top number.

However, all the options they give are all OVER 1. None of them can possibly be the right solution.

The only thing I can think is that I'm missing a font or somehow not displaying properly. I must be missing something, because it doesn't make any sense.

I agree with you. Every answer there is equal to or higher than 2 even. Even at the quickest glance it's more than obvious the answer is <1.

This is exactly why I hate it when teachers make their own tests. They should at least have someone backcheck their work first.. lol.

I dont know how many times I had to correct the teacher's on their own math/engineering tests when I was in college and high school.

It usually took 30min to make them show me how they came up with the answer. Usually thats where they realize that they forgot to invert something. ;)

2^9/5 is 2^1.8 there's nothing there that is smaller than 1. Also you can never have any positive number with a positive power and come up with a number smaller than 1. 2^1/100000000 is larger than 1. Even if they are negative powers the answers still dont work.

[wilkin250r]

Originally posted by 400exrules
like, simplyfying radicals with fraction exponents.

here's a practice quiz from the chapter/section of my book to show you what im talking about

i have a quiz on it monday and i dont understand a lick of it. My teacher is horrible at teaching, everyones failing his class.
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Give me a specific problem that you are struggling with, and I can help.

I can't just "teach" you about radicals, it's far too broad and general. I would have to write pages and pages, and you already have that in front of you (your textbook).

However, I CAN help you with one specific problem, and also give you rules and hints that would apply to other problems just like it.

[PWM_330EX]

Originally posted by bwamos

2^9/5 is 2^1.8 there's nothing there that is smaller than 1. Also you can never have any positive number with a positive power and come up with a number smaller than 1. 2^1/100000000 is larger than 1. Even if they are negative powers the answers still dont work.

I don't know what the original question was & not to confuse the issue but the order of operations is:

1) powers
2) mult & div
3) add & sub

Since there are no parenthesis in 2^9/5, you'd do the power operation first then the division so it'd be (2^9)/5 =102.4

To get 2^1.8 as an answer, the problem would need to be stated as 2^(9/5)=3.48