geometry perimeter and area

[malloryt]

I have a Test on irregular rectangles,they are like two shapes in one. Anyway, I am having trouble finding out how you find the area and perimeter and I just get stuck. I can do the plain rectangles , but we're learning these and I can't find the answer to my qustion anywere.

 

[mmm4444bot]

Are you sure you do not mean irregular polygons ?

The only regular rectangles are squares because all sides of those rectangles are equal.

In other words, all non-square rectangles are irregular. You find their perimeter and area using the famous formulas:

Perimeter = 2 * (Length + Width)

Area = Length * Width

When you say that irregular rectangles have "two shapes in one", do you mean that you can divide an irregular rectangle into a square and smaller irregular rectangle ?

 

[adnanr198]

You might be thinking about a golden rectangle
You might want to try searching that on google

 

[Mrspi]

I might as well add my two cents to the speculations about what kind of problem this poster is referring to.....

Maybe something like this? (This is a VERY simple version of the type of problem I think you mean)

____________
|           |
|           |_________
|                     |
|                     |
|_____________________|

If this is the kind of problem you're talking about, the general approach is to divide the figure up into "manageable" parts....perhaps like this.....

____________
|           |
|___________|_________
|                     |
|                     |
|_____________________|

Once you've done something like this, it is often possible to find missing lengths which can be used to find perimeters and areas.

 

[mmm4444bot]

malloryt, the only definition that you posted for "irregular rectangles" is "they are like two shapes in one".

That definition is inadequate.

I'm still thinking that you mean an irregular four-sided shape, like a rectangle with different triangles stuck on to one or more sides.

But, perhaps it's simpler than that. Maybe you mean shapes that are built solely from rectangles, by sticking different rectangles together.

Either way, calculating the perimeter is as easy as determining the lengths of all line sgements, distinguishing between line segments that are part of the perimeter versus not part of the perimeter, and adding the relevant segments together.

With area, you divide the shape up into smaller shapes whose area you can determine, and then add up all the sub-areas to get the total area.

In short, you need to decompose the shape into familiar objects, like rectangles, squares, and triangles. You know how to deal with those shapes.

And, most certainly, if you do not have a picture, draw one !

 

[Deleted member 4993]

My two cents:

I think the poster meant "irregular quadrilateral" - which can be always divided into two triangles.

Notice that the poster did not say "boo" after the original post .. . must be studying for the test....