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September 14th, 2019, 12:27 PM  #1 
Newbie Joined: Sep 2019 From: New York Posts: 3 Thanks: 0  Proof for a challenging inequality
I have something I believe to be true, but I'm uncertain, so I'm looking for a proof. For positive real numbers a,b,c,d Prove that if a>=b and c<=d, then a/c <= b/d Last edited by bluekaterpillar; September 14th, 2019 at 12:30 PM. 
September 14th, 2019, 01:12 PM  #2 
Global Moderator Joined: May 2007 Posts: 6,835 Thanks: 733 
$ad\ge bc$, since $a\ge b$ and $d\ge c $. Divide both sides by $dc$ and get $\frac{a}{c} \ge \frac{b}{d}$.

September 14th, 2019, 01:17 PM  #3 
Newbie Joined: Sep 2019 From: New York Posts: 3 Thanks: 0 
Thanks! I can't believe I missed that.


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