UGH! 8th Grade Math

[ttaylor508]

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!

[Veronica]

What's the question?

[ttaylor508]

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?

[solobiker]

give me a minute. Asking my DH who loves math

[solobiker]

Area= LxW

980=LxW

4L=5W ratio of length to width

4/5L=W solving for W

980=Lx4/5L solve for L

[ttaylor508]

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?

[solobiker]

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

[ttaylor508]

Area= LxW

980=LxW

4L=5W ratio of length to width

4/5L=W solving for W

980=Lx4/5L solve for L

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

[Veronica]

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

[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

[Biciclista]

solo biker gets the star.

[ttaylor508]

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

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.

[solobiker]

solo biker gets the star.

[Veronica]

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

Veronica

[solobiker]

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

Veronica

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