My Math Forum An electronics assembly consists of two independent sub syst

 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

,

,

,

,

,

,

,

# 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 Display Modes Linear 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