
Probability and Statistics Basic Probability and Statistics Math Forum 
 LinkBack  Thread Tools  Display Modes 
May 12th, 2013, 03:12 AM  #1 
Member Joined: Feb 2013 Posts: 44 Thanks: 0  Probability problem
OK so there's 80 light bulbs 6 are defective, which means 74 are not defective. If I select 2 at random, what are the odds at least one is defective. the answer key says. 1 C(74,2)/ C(80,2) = 1 74x73/80x79 = .145 I don't understand the answer key at all. I thought to use a stemgraph ( a line with more lines protruding from that line, shwoing the varous probabilites of otcomes.)) can someone explain please? 
May 12th, 2013, 04:51 AM  #2  
Math Team Joined: Dec 2006 From: Lexington, MA Posts: 3,267 Thanks: 408  Re: Probability problem Hello, hamburgertime! Quote:
The opposite of "at least one defective? is "NO defective". What is the probability of no Defective (both are Good)? There are:[color=beige] .[/color] possible pairs of bulbs. There are:[color=beige] .[/color] pairs of Good bulbs. ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ It could be solved like this . . . There are three possible scenarios:  

Tags 
probability, problem 
Thread Tools  
Display Modes  

Similar Threads  
Thread  Thread Starter  Forum  Replies  Last Post 
Probability Problem / Insurance problem  bsjmath  Advanced Statistics  2  March 1st, 2014 02:50 PM 
Probability problem  ystiang  Advanced Statistics  1  February 13th, 2014 04:27 PM 
Probability problem  halloweengrl23  Advanced Statistics  3  March 23rd, 2012 02:27 AM 
Probability Problem.Please help  adiptadatta  Probability and Statistics  1  May 11th, 2010 06:46 AM 
Help with probability problem!  indian  Algebra  0  February 21st, 2008 04:10 PM 