area of rectangle given internal dimensions and distance to external.

[jijoe]

I'm trying to get my head round this, I've tried various things but I'm afraid I'm just not mathematically minded. To put this into context I'm a trainee construction estimator (may have chosen the wrong profession), I have the dimensions of an internal brick wall and the distance between it and another external brick wall. I need the area of the rectangle from the external wall.

Included a quick example. So I'm after the area of the rectangle shaded in orange given only internal dimensions and a distance to the external.

Many Thanks!

 

[stapel]

I'm trying to get my head round this, I've tried various things but I'm afraid I'm just not mathematically minded. To put this into context I'm a trainee construction estimator (may have chosen the wrong profession), I have the dimensions of an internal brick wall and the distance between it and another external brick wall. I need the area of the rectangle from the external wall.

Included a quick example.

*---------------------------*
|                           |
|  *---------------------*  |
|  |                ^    |  |
|  |<---10----------|--->|  |
|  |                |    |  |
|  |               5|    |  |
|  |                v    |  |
|  *---------------------*  |
|                0.5        |
*---------------------------*

So I'm after the area of the rectangle shaded in orange given only internal dimensions and a distance to the external.

Why can't you just add the distance between to the internal dimensions to get the external dimensions, and then multiply to get the external area? (Or, if you're referring to the area between the two walls, why can't you do the above, and then subtract out the internal area?)

Please be specific. Thank you!