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Homework Help: Conditional Probability Traffic light question

  1. Oct 13, 2005 #1
    Hey guys Me and my friend just got this question and it seems easy but i just want to make sure we are right anyway here it is:

    A road has two stoplights at consecutive intersections. The prob. of a red at the first is 0.55 and the probability of a green at the second, give a green at light oine is .75

    Find the prob of a green at both intersections:
    Givens = (r1 = .55) (g2|g1=.75)
    now i believe its simply as just r1*.75.

    which is like .33

    Anybody know if i did this right?

  2. jcsd
  3. Oct 13, 2005 #2
    In your problem statement:

    [itex]P(r_1 )=0.55[/itex] and [itex]P(g_2 |g_1 )=0.75[/itex]

    but I don't know how you got your answer because .55*.75 = .4125, though I do agree that .33 is very close to the answer, depending on how you round the decimal.
  4. Oct 14, 2005 #3
    Hint: http://mathworld.wolfram.com/ConditionalProbability.html" [Broken].
    Just use the formula.
    Last edited by a moderator: May 2, 2017
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