 My Math Forum An electronics assembly consists of two independent sub syst
 User Name Remember Me? Password

 Algebra Pre-Algebra and Basic Algebra Math Forum

 October 10th, 2013, 05:02 AM #1 Senior Member   Joined: Oct 2009 Posts: 895 Thanks: 1 An electronics assembly consists of two independent sub syst 1) An electronics assembly consists of two independent sub systems A and B > From previous testing procedures, the following probabilities are known p(A fails) = 0.2 , p(B fails) = 0.19 , P(A fails or B fails) = 0.18 Find the probability that both A and B fail. 2) The probability that a student owns a car is .65 and the probability that a student owns a computer is .82. If the probability that a student owns both is .55, what is the probability that both A and B fail? 3) A box contain 4 bad 6 good tubes. Two are drawn from the box at a time. What is the probability that both tubes drawn are good? Please can help me to solve this question. I need clear out the answer with explanation. October 10th, 2013, 08:01 AM #2 Global Moderator   Joined: Dec 2006 Posts: 20,921 Thanks: 2203 1) P(A fails & B fails) = P(A fails) + P(B fails) - P(A fails or B fails) = 0.2 + 0.19 - 0.18 = 0.21. 2) You have typed the question incorrectly, as A and B have not been defined. � � P(student owns a car or computer) = 0.65 + 0.82 - 0.55 = 0.92. 3) If each tube available is equally likely to be drawn and two distinct tubes are drawn, � � the required probability = (6/(6+4))(5/(5+4)) = 1/3. � � (When first is chosen, 6 of 10 are good. After a good tube has been drawn, � � 5 good tubes remain amongst the 9 still available to be drawn.) October 10th, 2013, 09:06 AM   #3
Senior Member

Joined: Jun 2013
From: London, England

Posts: 1,316
Thanks: 116

Re: An electronics assembly consists of two independent sub

Quote:
 Originally Posted by r-soy 1) An electronics assembly consists of two independent sub systems A and B > From previous testing procedures, the following probabilities are known p(A fails) = 0.2 , p(B fails) = 0.19 , P(A fails or B fails) = 0.18 Find the probability that both A and B fail.
There are two things wrong with this question:

1) If A and B are independent, then P(A and B) = P(A)P(B) and P(A or B) = P(A) + P(B) - P(A)P(B).

2) In any case, P(A or B) cannot be less than P(A) or P(B). October 11th, 2013, 10:56 PM #4 Senior Member   Joined: Oct 2009 Posts: 895 Thanks: 1 Re: An electronics assembly consists of two independent sub 2) The probability that a student owns a car is .65 and the probability that a student owns a computer is .82. If the probability that a student owns both is .55 what is the probability that a given student owns neither a car nor a computer? What does that mean (what is the probability that given student owns neither a car nor a computer) and what is the formula here ... and what if here written either instead of neither? October 11th, 2013, 11:39 PM #5 Global Moderator   Joined: Dec 2006 Posts: 20,921 Thanks: 2203 The question "what is the probability that a given student owns neither a car nor a computer" means "what is the probability that a given student does not own a car and does not own a computer". The question would be ungrammatical if "neither" were changed to "either". P(student does not own a car and does not own a computer) = 1 - P(student owns a car or a computer) = 1 - 0.92 = 0.08. October 12th, 2013, 12:08 AM #6 Senior Member   Joined: Oct 2009 Posts: 895 Thanks: 1 Re: An electronics assembly consists of two independent sub Thanks so so much. October 15th, 2013, 12:02 AM #7 Senior Member   Joined: Jun 2013 From: London, England Posts: 1,316 Thanks: 116 Re: An electronics assembly consists of two independent sub Another way to think about it is to consider a typical 100 students: 55 own both a car and a computer Another 10 own a car (but no computer) (making 65 in all who own a car) Another 27 own a computer (but no car) (making 82 in all who one a computer) Leaving 8 who own neither. Tags assembly, consists, electronics, independent, syst Search tags for this page
,

,

,

,

,

,

,

# an electronics assembly consists of two independent sub systems a and b. from previous testing procedures, the following probabilities are known. p( a fails)= 0.2, p( b fails)=0.19, p (a fails or b fails) = 0.18. find the probability that both a and b fai

Click on a term to search for related topics.
 Thread Tools Show Printable Version Email this Page Display Modes Linear Mode Switch to Hybrid Mode Switch to Threaded Mode Similar Threads Thread Thread Starter Forum Replies Last Post gelatine1 Computer Science 0 September 25th, 2013 04:59 AM mathismydoom Algebra 5 October 11th, 2012 03:27 AM BenM Real Analysis 2 July 26th, 2011 02:58 AM varunnayudu Advanced Statistics 2 November 27th, 2010 08:08 PM conradtsmith Calculus 1 August 20th, 2009 04:36 AM

 Contact - Home - Forums - Cryptocurrency Forum - Top

Copyright © 2019 My Math Forum. All rights reserved.       