# Thread: i need help

1. ## i need help

How can the surface area of a rectangular prism change if evey one of the dimensions is increased by a factor of x? and how can we prove that?

2. If you are going to ask us for help, give your topic a meaningful subject line. "i need help" says nothing about what kind of problem you are having.
Originally Posted by rose1
How can the surface area of a rectangular prism change if evey one of the dimensions is increased by a factor of x? and how can we prove that?
Take any rectangular prism. Let the lengths of the sides (width, height, and length) be $u,\,v,$ and $w.$ Then what is the surface area of this prism? It is just the sum of the areas of each face:

$S=2uv+2vw+2uw.$

If you increase each dimension by a factor of $x$, then the new dimensions are $ux,\,vx,$ and $wx.$ So what will the new surface area be? Now compare this to that of the original.