20060525, 16:21  #1 
Bronze Medalist
Jan 2004
Mumbai,India
4004_{8} Posts 
Aliens.
100 aliens attended the Intergalactic meeting on Earth. 73 had 2 heads 28 had 3 eyes. 21 had four arms. 12 had 2 heads and 3 eyes. 9 had 3 eyes and 4 arms. 8 had 2 heads and 4 arms. 3 had all 3 unusual features. How many had none of these unusual features.? Mally 
20060525, 17:04  #2 
Aug 2002
Buenos Aires, Argentina
1,423 Posts 
My solution is:
A = 1 head, 2 eyes, 2 arms B = 1 head, 2 eyes, 4 arms C = 1 head, 3 eyes, 2 arms D = 1 head, 3 eyes, 4 arms E = 2 heads, 2 eyes, 2 arms F = 2 heads, 2 eyes, 4 arms G = 2 heads, 3 eyes, 2 arms H = 2 heads, 3 eyes, 4 arms 100 = A+B+C+D+E+F+G+H 73 = E+F+G+H 28 = C+D+G+H 21 = B+D+F+H 12 = G+H 9 = D+H 8 = F+H 3 = H A = ? D = 93 = 6 F = 83 = 5 G = 123 = 9 C = 28693 = 10 B = 21653 = 7 E = 73593 = 56 A = 100710656593 = 4 So the requested number of aliens is four. 
20060525, 18:39  #3 
Jun 2003
11000110011_{2} Posts 
This is a simple question of sets. Add all the 3 sets, subtract the overlaping. My answer is 4. Last fiddled with by Citrix on 20060525 at 18:40 
20060525, 19:10  #4 
Aug 2002
Buenos Aires, Argentina
2617_{8} Posts 
I found the drawing features of Tex very interesting:
Sorry but spoiler and tex tags are incompatible. 
20060525, 22:28  #6  
Aug 2002
20334_{8} Posts 
Quote:


20060526, 01:22  #7 
May 2004
New York City
10213_{8} Posts 
Using the InclusionExclusion Principle, the answer can be
immediately computed as: 100  (73+28+211298+3) == 100  96 == 4  davar55 
20060526, 07:10  #8 
Bronze Medalist
Jan 2004
Mumbai,India
2^{2}×3^{3}×19 Posts 
Aliens.
All the answers given above are correct. The Venn diagram given by Alpetron was what I was in search of but do not know how to use Tex. These were followed up by Mike and Vctor. Citrix and Davar gave the short cuts. Thanks to you Davar Im happy that you are now flexing your muscles! Inclusion  Exclusion principle ? One for my note book! Mally 
Thread Tools  
Similar Threads  
Thread  Thread Starter  Forum  Replies  Last Post 
No aliens detected by SETI because radio sucks?  jasong  jasong  9  20130114 09:53 