# Simple math question

Discussion in 'Math' started by tadm123, Feb 7, 2014.

Nov 20, 2013
43
0
In an engineering lecture I'm stuck in this part, this is one of those problems where you know it is pretty dumb but can't get out of it. Here's the link:

http://s18.postimg.org/ytzfn0wnt/equation.jpg

Can anyone explain me how they got a simplified Re/re from there?

I divided both of the numbers in that equation and got a (Re+re)/re.
How did they get rid of that "re" in the numerator and simplify it in that form?

Last edited: Feb 7, 2014
2. ### MrChips Moderator

Oct 2, 2009
12,418
3,355
(Re + re)/re = Re/re + 1

But I get

Re/re + 1 >= 2.3716

Re/re >= 1.3716

3. ### shteii01 AAC Fanatic!

Feb 19, 2010
3,378
494
$\frac{Re+re}{re}\geq\frac{27*13}{10*14.8}$
$\frac{Re}{re}+\frac{re}{re}\geq\frac{351}{148}$
$\frac{Re}{re}+1\geq2.372$
$\frac{Re}{re}\geq2.372-1$
$\frac{Re}{re}\geq1.372$