Help!

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doodle
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Help!

Post by doodle » Thu Apr 23, 2015 9:41 am

Trying to help kid with math problem and stuck....need help.

Need to solve for N

143 + (3.90 x N) / 26 + N = 4.89
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Re: Help!

Post by WiseOne » Thu Apr 23, 2015 9:53 am

Can't resist....

Step 1:
3.9N/26 + N = 4.89 - 143

Step 2:
3.9N + 26N = 26 x (4.89 - 143)

Step 3:
29.9N = 26 x (4.89 - 143)

Step 4:
N = (26 x (4.89 - 143))/29.9

Voila.
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Re: Help!

Post by doodle » Thu Apr 23, 2015 9:54 am

The Answer is supposed to be 16  :-\
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Re: Help!

Post by dragoncar » Thu Apr 23, 2015 9:55 am

1) subtract 143 from both sides:

(3.90 x N) / 26 + N = 4.89 - 143 = -138.11

2) multiply both sides by 26

26( (3.90 x N) / 26 + N ) = 26*-138.11 = -3590.86

3) distribute 26 outside of parens

26(3.90 x N) / 26 + 26*N =  3.9N+26N = 28.9N = -3590.86

4) divide both sides by 29.9

N = -120.10

too bad Wolfram Alpha has a subscription now to see calculation steps
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doodle
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Re: Help!

Post by doodle » Thu Apr 23, 2015 9:57 am

If you plug 16 into the equation for N though it comes out to 4.89
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Re: Help!

Post by dragoncar » Thu Apr 23, 2015 9:59 am

doodle wrote: If you plug 16 into the equation for N though it comes out to 4.89
How so?  I'm really trying to figure out where you left out the parens

edit: I figured it out:

(143 + (3.90 x N)) / (26 + N) = 4.89
Last edited by dragoncar on Thu Apr 23, 2015 10:01 am, edited 1 time in total.
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Re: Help!

Post by hoost » Thu Apr 23, 2015 10:03 am

Yes, seems like parentheses are missing somewhere.
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Re: Help!

Post by doodle » Thu Apr 23, 2015 10:07 am

Here is the problem....

John works in a tea shop.  A customer comes in and wants a mixture of two teas, Chamomile tea and Lavender tea.  The customer buys 26 ounces of lavender tea at $5.50 an ounce. The Chamomile tea is $3.90 an ounce. The mixture of the two teas comes out to $4.89 an ounce. How many ounces of Chamomile tea did the customer buy? 
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Re: Help!

Post by moda0306 » Thu Apr 23, 2015 10:08 am

I don't know what the right answer is, but all the wrong answers are Obama's fault.
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Re: Help!

Post by dragoncar » Thu Apr 23, 2015 10:09 am

dragoncar wrote:
doodle wrote: If you plug 16 into the equation for N though it comes out to 4.89
How so?  I'm really trying to figure out where you left out the parens

edit: I figured it out:

(143 + (3.90 x N)) / (26 + N) = 4.89
1) multiply both sides by 26+N

143 + 3.9N = (26+N)4.89 = 26*4.89 + 4.89N

2) subtract 3.9N from both sides

143 = 127.14 + .99N

3) subtract 127.14 from both sides

15.86 = .99N

4) divide both sides by .99

16.(02)~ = N
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Re: Help!

Post by hoost » Thu Apr 23, 2015 10:09 am

dragoncar wrote:
edit: I figured it out:

(143 + (3.90 x N)) / (26 + N) = 4.89
^^ Well done.

(143 + (3.9 x N)) = (26 + N) * 4.89

143 + (3.9 x N) = 4.89*26 + 4.89*N

143 - 4.89*26 = 4.89*N - 3.9*N

N = (143 - 4.89*26) / (4.89 - 3.9) = 16.02
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Re: Help!

Post by Ad Orientem » Thu Apr 23, 2015 10:13 am

My brain hurts. I need to lie down.
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Re: Help!

Post by Pointedstick » Thu Apr 23, 2015 11:07 am

Ad Orientem wrote: My brain hurts. I need to lie down.
And you say kids these days have it easy educationally! My brain hurts too.
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Mountaineer
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Re: Help!

Post by Mountaineer » Thu Apr 23, 2015 12:38 pm

Pointedstick wrote:
Ad Orientem wrote: My brain hurts. I need to lie down.
And you say kids these days have it easy educationally! My brain hurts too.
They do.  It's the adults on this forum with the problem.  ;)

... Mountaineer
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Re: Help!

Post by dualstow » Thu Apr 23, 2015 6:15 pm

I'm offended by the shitty subject line.
Anyway, I did it like this:

y = number of ounces of chamomile where
3.9y = amount spent on chamomile
26+y = total ounces of all tea bought and
143 = amount spent on lavender // good god. 26 * $5.50
TOTAL OUNCES * AVG PRICE (or $4.89) = TOTAL SPENT
---------------------------------------------------------------
(26+y) *4.89 = (143+3.9y)
127.14+4.89y = "  "        // 26 * 4.89 = 127.14
4.89y = 3.9y + 15.86    // subtract from both sides (143-127.14=15.86)
.99y =15.86                    // subtract 3.9y from both sides
y=16.02                        //  (15.86 ÷ .99)

That's a lotta tea.

(edited in side notes)
(edited in algebra labels at top)
(edited in colors. I'm really procrastinating now, since you've solved it hours ago)
Last edited by dualstow on Thu Apr 23, 2015 6:42 pm, edited 1 time in total.
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Re: Help!

Post by barrett » Thu Apr 23, 2015 7:06 pm

dualstow wrote: I'm offended by the shitty subject line.
The problem is shittier than the subject line! Any kid who comes up with 16.020202... is going to assume it's the wrong answer. I do miss obsessing about this stuff with my daughter. We used to try to solve problems like this over the phone when I was on the road, and the parentheses would always get in the wrong place.
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Re: Help!

Post by dualstow » Thu Apr 23, 2015 7:35 pm

barrett wrote: The problem is shittier than the subject line! Any kid who comes up with 16.020202... is going to assume it's the wrong answer.
From the subject line, I was hoping it was going to be about the Beatles album. Imagine my disappointment.

Well, the actual word problem came much later than the problem originally presented. Therefore, we should go beyond algebra and assume that x = what stone didn't originally tell us*, which may = the word problem (y) + more detailed instructions (z).
If z is greater than zero, I posit that z = something like "use a No.2 pencil" & "round to the nearest integer".

(*No offense, stone. I know you were just getting to the heart of the matter quickly).
I do miss obsessing about this stuff with my daughter. We used to try to solve problems like this over the phone when I was on the road, and the parentheses would always get in the wrong place.
That sounds difficult to do over the phone. I hope you were in a hotel room and not driving while doing distributive multiplication!  :)
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Re: Help!

Post by doodle » Thu Apr 23, 2015 9:20 pm

Thanks for all the help! You might be surprised that this was actually a practice question on the GED math test......they recently updated the test in 2014 and the math portion got a lot more challenging
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Re: Help!

Post by moda0306 » Thu Apr 23, 2015 9:21 pm

doodle,

If you're not kidding, I have a lot to rethink in my life.
"Men did not make the earth. It is the value of the improvements only, and not the earth itself, that is individual property. Every proprietor owes to the community a ground rent for the land which he holds."

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Re: Help!

Post by doodle » Thu Apr 23, 2015 9:30 pm

Dont feel bad. One of my friends is an ER doctor. He took the math test on a challenge from me and failed it. They have lengthened the time for the test, but it is still challenging.

Tutoring for this test really hammered home how hard it is for a certain segment of society to keep up. We are moving at a breakneck speed into a complex future and my experiences with students makes me wonder how many will be able to participate
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Re: Help!

Post by dualstow » Thu Apr 23, 2015 10:45 pm

TennPaGa wrote: No offense?  Possibly stone would be offended.  After all, he made no posts in this thread ! :)
LOL.  doodlestone. Sounds kind of like my name. Maybe that's a blind spot for me. Although I couldn't separate Reub from notsheigetz for a while, and they are quite different.
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Re: Help!

Post by Benko » Fri Apr 24, 2015 7:10 pm

doodle wrote: Dont feel bad. One of my friends is an ER doctor. He took the math test on a challenge from me and failed it. They have lengthened the time for the test, but it is still challenging.

Tutoring for this test really hammered home how hard it is for a certain segment of society to keep up. We are moving at a breakneck speed into a complex future and my experiences with students makes me wonder how many will be able to participate
I don't understand.  Why do most people need to be able to do these algebra problems?    These seem irrelevant for most people i.e. unrelated to what most adults need to be able to do.

If you've gone through algebra the tea merchant  and the original problem in this thread are straightforward, but I don't think it reflects at all on those who can't.
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Re: Help!

Post by moda0306 » Fri Apr 24, 2015 7:38 pm

I think algebra trains your brain to rearrange and break down problems into their more basic parts, so you can figure out a solution.

I think that, by its very nature, enables critical thinking at a more efficient level.
"Men did not make the earth. It is the value of the improvements only, and not the earth itself, that is individual property. Every proprietor owes to the community a ground rent for the land which he holds."

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Re: Help!

Post by dualstow » Fri Apr 24, 2015 8:44 pm

Benko wrote:
doodle wrote: Dont feel bad. One of my friends is an ER doctor. He took the math test on a challenge from me and failed it.
...
I don't understand.  Why do most people need to be able to do these algebra problems?    These seem irrelevant for most people i.e. unrelated to what most adults need to be able to do.
...
People tend to speak negatively about tests with answers that are soon forgotten. Especially the students themselves. I mean, why do children have to learn state capitals or details of the Civil War? Still, I believe some basics are important before you get down to acquiring specialized skills.

All I know is, I wouldn't want to hire someone who doesn't know how to eat an artichoke, and I wouldn't want to hire someone who doesn't know who Abe Lincoln is or who has had a length of time to learn algebra problem-solving (months) and still can't do it. The ER doctor could do it after a refresher course.
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Re: Help!

Post by Benko » Sat Apr 25, 2015 12:24 pm

moda0306 wrote: I think algebra trains your brain to rearrange and break down problems into their more basic parts, so you can figure out a solution.

I think that, by its very nature, enables critical thinking at a more efficient level.
I had algebra and 3 semesters of calculus.  While I was proficient at that, I don't know that it did anything for my ability to think critically.  Critical thinking (unlike algebra) is a skill that would be helpful to everyone, and it should be taught to everyone.  OTOH perhaps teaching critical thinking in not in the interests of the educational establishment. 
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