course Mth 152 ·???m·h·y??|}???Xz=???assignment #007
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08:00:53 12.2.6 single die, p(odd or <5). What is the probability of getting an odd result or a result < 5?
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RESPONSE --> 3/6 + 4/6 - 2/6 = 5/6 odd + less than 5 - the union = 5/6
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08:22:25 12.2.6 single die, p(odd or <5). What is the probability of getting an odd result or a result < 5?
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RESPONSE -->
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08:23:17 ** there are 3 possible odd outcomes and four outcomes less that 5 which would add up to 7 outcomes, except that 2 of the outcomes < 5 are alrealdy odd and won't be counted. Thus the number of outcomes which are odd or less that 5 is 3 + 4 - 2 = 5 (this expresses the rule that n(A U B) = n(A) + n(B) - n(A ^ B), where U and ^ stand for union and intersection, respectively ). Thus the probability is 5/6. In terms of the specific sample space: The sample space for the experiment is {1, 2, 3, 4, 5, 6}. Success corresponds to events in the subset {1, 2, 3, 4, 5}. There are 6 elements in the sample space, 5 in the subset consisting of successful outcomes. Thus the probability is 5/6. **
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RESPONSE --> ok
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10:07:48 Query 12.2.15 drawing neither heart nor 7 from full deck
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RESPONSE --> probability is number of hearts plus number of sevens minus union of these: 13/52 + 4/52 - 1/52 = 4/13 it's complement is the answer: 9/13 odds in favor are 9:4
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10:09:16 ** The sample space consists of the 52 cards in a full deck. There are 39 cards that aren't hearts, four 7's but only three aren't hearts so there are 36 cards that aren't hearts or seven. The probability is therefore 36/52 = 9/13. The odds in favor of the event are 16 to 36 (number favorable to number unfavorable), which in reduced form is 4 to 9. **
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RESPONSE --> I got it right!
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10:17:12 12.2.24 prob of black flush or two pairs
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RESPONSE --> prob. of black flush is 2554/2598960 + 123,552/2,598,960(prob. of 2 pair) = 126,106/2,598,960 which equals .048522
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10:19:07 ** There are C(13,5) = 1287 ways to get a flush in a given suit--gotta choose the 5 cards from the 13 cards in that suit. There are two black suits so there are 2 * 1287 = 2574 possible black flushes. As the text tells you there are 123,552 ways to get two pairs. You can incidentally get this as 13 * C(4, 2) * 12 * C(4, 2) * C(44, 1) / 2 (2 of the 4 cards in any of the 13 denominations, then 2 of the 4 cards in any of the remaining 12 denominations, divide by 2 because the two denominations could occur in any order, then 1 of the 44 remaining cards not in either of the two denominations. There is no way that a hand can be both a black flush and two pairs, so there is no overlap to worry about (i.e., n(A and B) = 0 so n(A or B) = n(A) + n(B) - n(A and B) = n(A) + n(B) ). Thus there are 123,552 + 2574 = 126,126 ways to get one or the other. The probability is therefore 126,126 / 2,598,960 = .0485, approx. **
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RESPONSE --> I got it differently but I got the same answer.
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10:29:01 12.2.33 x is sum of 2-digit numbers from {1, 2, ..., 5}; prob dist for random vbl x
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RESPONSE --> You would have to start with 3 , the smallest sum and end with 9, the greatest sum. if x = 3,4,5,6,7,8,9 then P(x)=.1,.1,.2,.2,.2,.1,.1 respectively (I listed all possible sums of x and divided each by total numbers possible(20) to get P(x).
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10:30:48 ** If 2 different numbers are chosen from the set (1, 2, 3, 4, 5} then the sum 3 can appear only as 1+2. 4 can appear only as 1+3, assuming numbers can't be repeated (so, for example, 2+2 is not allowed). 5 can occur as 1+4 or as 2+3. 6 can occur as 1+5 or as 2+3. 7 can occur as 2+5 or as 1+6. 8 can occur only as 3+5. 9 can occur only as 4+5. Of the 10 possible combinations, the sums 3, 4, 8 and 9 can occur only once each, so each has probability .1. The sums 5, 6 and 7 can occur 2 times each, so each has probability .2. The possible sums are as indicated in the table below. 1 2 3 4 5 1 3 4 5 6 2 5 6 7 3 7 8 4 9 This assumes selection without replacement. There are C(5, 2) = 10 possible outcomes, as can be verified by counting the outcomes in the table. 3, 4, 8 and 9 appear once each as outcomes, so each has probability 1/10. 5, 6 and 7 appear twice each as outcomes, so each has probability 2/10. x p(x) 3 .1 4 .1 5 .2 6 .2 7 .2 8 .1 9 .1 **
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RESPONSE --> I got it right!
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13:53:02 Query 12.2.36 n(A)=a, n(S) = s; P(A')=? What is the P(A')?
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RESPONSE --> P(A)=s - a
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13:57:20 ** A' is everything that is not in A. There are a ways A can happen, and s possibilities in the sample space S, so there are s - a ways A' can happen. So of the s possibilities, s-a are in A'. Thus the probability of A' is P(A') = n(A') / n(S) = (s - a) / s. **
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RESPONSE --> I see I didn't divide by s to get the probability.
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14:05:43 Query 12.2.42 spinners with 1-4 and 8-10; prob product is even
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RESPONSE --> I made a ""tree"" and found that 10 out of 12 products are even which is 5/6=.8333333333"