+0  
 
+5
117
1
avatar

number of unique triad combinations equals 528. 

What is the number of unique items that makes a total of 528 unique combinations (order does not count as a combination, so ABC is the same combination as CAB)?

I found a formula for finding the number of combinations for a specified number of unique items when the number of items in a set is also specified, however that formula uses factorials and I don't know how to work around that when I don't know one of the variables.

Guest Mar 17, 2017
Sort: 

1+0 Answers

 #1
avatar+4710 
+3

I think this is basically your question:

\(528=\frac{n!}{3!(n-3)!}\)

And you're trying to solve for n.

 

I would just try plugging in different values for n until you find the right one.

First I tried 5, that gave me 10.

Next I tried 15, that gave me 455.

Next I tried 16, that gave me 560.

 

....Well...‚Äč I don't think that n should have a fraction....I don't know, but maybe this helps some anyway.

hectictar  Mar 17, 2017

10 Online Users

We use cookies to personalise content and ads, to provide social media features and to analyse our traffic. We also share information about your use of our site with our social media, advertising and analytics partners.  See details