All about flooble | fun stuff | Get a free chatterbox | Free JavaScript | Avatars    
perplexus dot info

Home > Numbers
Let's count (Posted on 2010-05-16) Difficulty: 3 of 5
How many subsets of (1; 2; 3; ... 14) have 15 as the sum of their largest and smallest elements in the subset?

See The Solution Submitted by Ady TZIDON    
Rating: 2.5000 (2 votes)

Comments: ( Back to comment list | You must be logged in to post comments.)
Some Thoughts re: solution (spoiler)- decimal spoiler Comment 2 of 2 |
(In reply to solution (spoiler) by Charlie)

Beautiful!

Still, staying decimal , one can  see it as a  gometric sequence <br>

with a(o)=4 and q=4 so the sum is (surprise,surprise ):<br>

 

(4^7 - 1) / (4-1)= 5461

isomorphic solution

Edited on May 16, 2010, 2:43 pm
  Posted by Ady TZIDON on 2010-05-16 13:58:09

Please log in:
Login:
Password:
Remember me:
Sign up! | Forgot password


Search:
Search body:
Forums (0)
Newest Problems
Random Problem
FAQ | About This Site
Site Statistics
New Comments (9)
Unsolved Problems
Top Rated Problems
This month's top
Most Commented On

Chatterbox:
Copyright © 2002 - 2017 by Animus Pactum Consulting. All rights reserved. Privacy Information