UGH! 8th Grade Math

So, my daughter has had the flu and missed school for the last several days and now she is frantically trying to make up the work she missed. She is totally stuck on a math problem and in tears. Unfortunately, her totally lame mother isn't much help in the math department. Even with my awesome googling skills, I am of little help to find the answer. Do any of you teachers out there have a good recommendation for a math reference book that we could use at home that would cover Junior High Math basics? Any help would be much appreciated!

What's the question?

The question was trying to find the length and width of a rectangle with the area of 980. The ratio of the length to width is 4 to 5.

Am I showing how lame I am in math?

give me a minute. Asking my DH who loves math

Area= LxW

980=LxW

4L=5W ratio of length to width

4/5L=W solving for W

980=Lx4/5L solve for L

Okay, I have been working on this problem for way too long, but I think I have it. So, the strategy I believe would be finding the units. So finding 4 x____=? and 5 x __=? for an area of 980. I started with units of 5 and just went up from there until I got to 7, so 28 x 35=980. Right? Is there an easier way though?

Hold on a second...doing some re-calcs

Quote:

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Originally Posted by solobiker

Area= LxW

980=LxW

4L=5W ratio of length to width

4/5L=W solving for W

980=Lx4/5L solve for L

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Thanks, I think yours explains it better. We must have been posting at same time. My head hurts now!

Awww... I just figured it out.

Another way...but probably not what the instructor intended... guess and check.

The ratio is 4/5. So think of equivalent fractions to 4/5, 8/10, 12/15. Keep going until you get to the pair that when you multiply them equals 980.


Or because it's a ratio

4L x 5L = 980
So 20L squared = 980
Lsquared = 49
L = 7

The lengths are 28 and 35.

Veronica

area = length x width
A= L x W

980= L x W

4L = 5W

solving for W -> 4/5L=W

substitute for W in area formula

980=L x 4/5 L

combine common terms

980 =4/5 L^2

divide both side by 5/4 to cancel terms

980/ (4/5) = L^2

1225 = L^2

take square roots of both sides

L= 35
solve for W from above

W=4/5 L when L=35...w= 28

check A=L x W area= 35 x 28 = 980 check

solo biker gets the star.

Quote:

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Originally Posted by solobiker

area = length x width
A= L x W

980= L x W

4L = 5W

solving for W -> 4/5L=W

substitute for W in area formula

980=L x 4/5 L

combine common terms

980 =4/5 L^2

divide both side by 5/4 to cancel terms

980/ (4/5) = L^2

1225 = L^2

take square roots of both sides

L= 35
solve for W from above

W=4/5 L when L=35...w= 28

check A=L x W area= 35 x 28 = 980 check

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Oh no....you lost me. See, I told you math was not my thing. I just don't remember doing this stuff in school, although I am sure I had to at some point. Thanks for input!!!! Daughter has now dried the tears and is happily moving onto the next problem. I am going to take an asprin.

Quote:

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Originally Posted by Biciclista

solo biker gets the star.

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:cool::cool:

The formula doesn't need to be so complicated because you know it's a ratio.

Veronica

Quote:

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Originally Posted by Veronica

The formula doesn't need to be so complicated because you know it's a ratio.

Veronica

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It's not that complicated, I just wrote out the solution algebraically.

Quote:

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Originally Posted by Veronica

4L x 5L = 980
So 20L squared = 980
Lsquared = 49
L = 7

The lengths are 28 and 35.

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L equals the unknown multiple for the ratio. Because it's a ratio you can go straight to my first step. I would have written algebraically if I could figure out how to put in an exponent.

Veronica

Quote:

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Originally Posted by Veronica

Another way...but probably not what the instructor intended... guess and check.

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A totally valid mathematical strategy. :cool:

Quote:

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Originally Posted by DirtDiva

A totally valid mathematical strategy. :cool:

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She possibly would have gotten points off for not showing her work.

There is that possibility, I suppose. But hey, what's wrong with:

4x5=20 but 20<980
24x30=720 but 720<980
32x40=1280 but 1280>980
28x35=980 so L=28 and W=35

unless specifically asked to work it out using algebra?

I'm guessing that the whole point is to learn algebra, not to find out what the length and width are :)

But hey, guessing is a working strategy in real life if you blank out on the algebra.

I need to lie down in a darkened room.

I don't know if the idea was to solve using algebra. The "new" math, as they call it, really tries to get kids to understand what they are doing, not to simply do the problem and get the right answer using a specific method. When my kids first started elementary, they had a meeting at the school to introduce the "new" math concept and why they are using it. I get whey they are teaching it this way, but I still don't understand all of the methods. I still use the traditional math that I was taught in school which totally confuses my kids when I try to help them. Luckily, DD is a good student and usually doesn't ask me for math help. I think she was just stuck because she had missed two days of lessons. The teachers is actually really great and I emailed her to tell her my daughter was struggling and she is going to sit down with her today.

Thanks for all of the help. I was totally at my wits ends yesterday trying to figure the problem out.

I think you are all off by 2x - A triangle is 1/2 of a square, the LxW=area applies to a square, not a triangle. In order to solve the problem, you must know that it is a right triangle as well.

NEVERMIND, my math skills are better than my reading skills, no one was talking about a triangle except me - everyone else was talking about a rectangle.

I'll guy bury my head in the sand now.

Here is a great website I found yesterday trying to help my son who is also eight grade with his algebra. You may not like it, but it's worth a look.


http://khanacademy.org/#Singapore%20Math

DDH-- awesome resource. thanks!

Moms I feel for you! A couple of years ago I studied to go into teaching, including taking the certification tests. I was only a couple of years removed from college algebra, statistics (two semesters) and calculus which I made 3 B's and an A in. But that test for middle school math was gut wrenching and included trigonometry, geometry, algebra! Hang in there, they made it to 8th grade only a few more years of math then they go to college where the math graduate students sponsor tutoring. :p

It cracks me up when my sister calls because she's having trouble helping my niece with her homework in 2nd grade. The new math is giving her fits.

I help with this stuff all day with people... that problem would completely stump many of my adult learners.

Yea, the goal of lots of math programs is to have them understand what's going on. However, the brutal fact is that sometimes the teacher doesn't. S/he's not going to say it... so s/he follows the book and hopes. I've seen it happen... they have no idea that they're asking a student to solve a quadratic equation.

Then there's when the teacher gets it and doesn't have any idea that while s/he is "teaching" understanding, what the studnets are getting are two things: a complex procedure taht they memorize anyway, because in fact they don't have the background to understand it as it's being taught and b: strong, repeated reinforcement of the idea that they are **supposed** to understand it, and therefore they must Not Be Good At Math because they don't.

It's a bit of a hot button for me 'cause I work with the victims all day...

They revamped the way numeracy was taught here about five to eight years ago, particularly at the primary/middle school level. Was it because the kids were failing? No, not really - it was because so many teachers needed upskilling.

http://curvebank.calstatela.edu/newmath/newmath.htm