# Non-Linear Modelling Concrete Slab Problem

• Oct 24th 2007, 08:52 PM
ollieman
Non-Linear Modelling Concrete Slab Problem
I hope someone can help me because i'm stumped

This problem is in the maths applied level 3 & 4.

The concrete slab in the shape of a rectangle shown on the right has an area of 63m^2. Form a Quadratic Equation and solve for "x" and then determine the width and length of the rectangle in order for it to be paved.

(you can't use trial and error or guessing)

http://img88.imageshack.us/my.php?im...entslabab0.jpg

Hope Someone can help me out

Cheers OLLiE
• Oct 25th 2007, 12:36 AM
ticbol
The slab is rectangle, so,
Area, A = 3x(x+4) = 63
3x^2 +12x -63 = 0
Divide both sides by 3,
x^2 +4x -21 = 0
Factoring,
(x +7)(x -3) = 0
x = -7 or 3 meters

Now I see what you mean by "in order for it to be paved"

The x = -7 meters cannot be measured because there are no negative measurements.

So, x = 3m

Therefore,
width = 3x = 3*3 = 9m.
lenght = (x +4) = (3 +4) = 7m.

Umm, again, therefore, width = 7 meters, and length = 9 meters. ---answer.
• Oct 25th 2007, 01:48 AM
ollieman
thanks ticbol
thanks heaps ticbol

I'm just not yet very good at written problems.
I'm sure you didn't even have to think to blink to work it out.

Cheers OLLiE