<p>Yep 30nCr2 would omit repeated couples, becuase its not talking about how many different ways you can arrange the plumbers in couples, but rather how many couples can be formed. Where plumber A and plumber B form couple AB which is the same as couple BA.</p>
<p>btw optimizerdad, I have always wanted to ask you, did you study anything math related, or are you just really fond of the subject? I'm asking becuase I constantly see you solve problems on these threads, which is awesome. I also wanted to thank you for you help with a couple of problems in the past ( one with logarithms and the other I don't remember).</p>
<p>Megaman123:
I'm an applied mathematician (yeah, people actually <em>pay</em> me to do this stuff). Did my undergrad in engineering (electronics), then a PhD in operations research. I specialize in combinatorial optimization - usually designing algorithms for scheduling problems in industry.</p>
<p>^Wow, that's actually very interesting.</p>
<p>^really! thats awesome. I'm probably gonna study econ., but who knows, maybe I'll be able to do engineering as well, I jsut hope I have the level to actually be able to manage studying for two degrees.</p>