Word problem:Rectangular feed lot

[silverdragon316]

This is my problem;

The width of a rectangular feed lot is 8m less than the length. The area is 20m^2. Find the length and width.

How shpuld I set this up?
What formula should I use?

1)What we want to know is the lenght and width.
2) we are given; feed lot is 8m less than the length and the area is 20m^2.
3) we should draw a rectangle

I know we have to label x

 

[axrw]

The formula for area of a rectangle is:

l * w = a

You could say that x is the length, and then express the width in terms of x knowing that it is 8 less than the length.

x(x - 8) = 20

Hopefully that helps.

 

[silverdragon316]

ok, here goes:

L.x.W=.A

......x(x-8)=20
.....x^2-8x=20
x^2-8x-20=0
..(x-10)(x+2)

x-10=0 or x+2=0
....x=10 or x=-2

SO, the width is 2 and the length is 10. (since -2 can't be an answer)

10x10x2x2=400
20m^2=400

am I right?

 

[jonboy]

You have found the L and W correctly. Good job!

 

[silverdragon316]

You have found the L and W correctly. Good job!

Thank you