# Math Help - Co-ordinate geometry minimum problem?

1. ## Co-ordinate geometry minimum problem?

The area of a rectangular block of land is 1000m2. If its length is x metres, find the block's dimensions if the perimeter is a minimum?

I have to solve the problem using a composite graph and finding its minimum rathert than using calculus. It would be appreciated if you could help me as I'm really not sure how to approach this

- iamapineapple

2. ## Re: Co-ordinate geometry minimum problem?

Letting $x$ be the length, I would then let $y$ be the width, $A$ be the area, and $P$ be the perimeter.

Can you give the area and perimeter in terms of $x$ and $y$?

3. ## Re: Co-ordinate geometry minimum problem?

Thank you, I am so silly. I got to the stage of making an equation for the perimeter but broke down because I didn't know what to let it equal to (i.e. thanks to you, I just let it equal P and then subbed values)!

Thanks, I got the (easy) answer!

4. ## Re: Co-ordinate geometry minimum problem?

Alternatively you can go as under:
Let length = x m
Perimeter P = 2 ( length + breadth ) = 2 ( x + 1000/x )
now you can take it forward.