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October 13th, 2012, 03:24 PM  #1 
Newbie Joined: Oct 2012 Posts: 4 Thanks: 0  I really need help in my probablities home work
I really need help with these math problems thank you everyone http://tinypic.com/view.php?pic=25ft4y9&s=6 http://tinypic.com/view.php?pic=2s7tnxe&s=6 http://tinypic.com/view.php?pic=2gucocj&s=6 http://tinypic.com/view.php?pic=35k2zd2&s=6 http://tinypic.com/view.php?pic=2r7yfqg&s=6 
October 13th, 2012, 03:34 PM  #2 
Newbie Joined: Oct 2012 Posts: 4 Thanks: 0  Re: I really need help in my probablities home work
I promise I'm not being lazy. I'm really lost and I'm desperate for help. Just clearing up because I put 5 questions at a time.

October 14th, 2012, 05:20 AM  #3 
Global Moderator Joined: Dec 2006 Posts: 20,301 Thanks: 1971 
You should be able to attempt at least one part of each question. If it makes it easier for some questions, suppose there is a population of 1000, say. If you are told that 20% have a certain description, that means 200 of the population fit the description. This can allow you to work with integers, which you may find easier. Find the size of the sample specified in the question and how many within that sample have the property specified (for which you have to calculate the probability), then divide the latter by the former. Can you post some attempts now?

October 14th, 2012, 12:00 PM  #4 
Senior Member Joined: Jul 2012 From: DFW Area Posts: 634 Thanks: 96 Math Focus: Electrical Engineering Applications  Re: I really need help in my probablities home work
I will try to help with the first one. For a. and b. if you read the problem the answers are explicitly given. For c. we have the following: probability = 0.06 + 0.63  0.028 = 0.662 . Why did I subtract off 0.028? To see why, let's follow the advice of [color=#00BF00]skipjack[/color] and assume 1000 cars. Of these cars, the number that need repair is 1000 * 0.06 = 60 . The number that were domestically manufactured is 1000 * 0.63 = 630 . However, the number of cars that are domestic or need repair is NOT 630 + 60 = 690. The reason is that the number of cars that need repair that were manufactured domestically is 1000 * 0.28 = 28, and this is counted in the 60. So we have to subtract off the 28. 60 + 630  28 = 662 and 662/1000 = 0.662 . I do not see question d. 

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