UGH! 8th Grade Math

[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

[solobiker]

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

[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.

[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

[Veronica]

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

The lengths are 28 and 35.

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

[DirtDiva]

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

A totally valid mathematical strategy.

[Cataboo]

A totally valid mathematical strategy.

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

[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?