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Unformatted text preview: Math 151 Midterm 1 Solutions 1. Suppose that 28 percent of the population drink tea, 35 percent drink coffee, 10 percent drink both. Find: ( i ) percentage of people who do not drink either. ( ii ) percentage of people who drink tea but not coffee Solution. (i) Answer: 47 percent (ii) Answer: 18 percent 2. Show that if events A, B, C are independent, then so are A and B C Solution. P ( A ( B C ) = P ( AB AC ) = P ( AB ) + P ( AC ) P ( ABC ) = P ( A ) P ( B ) + P ( A ) P ( C ) P ( A ) P ( B ) P ( C ) = P ( A )[ P ( B ) + P ( C ) P ( BC )] = P ( A ) P ( B C ) In above steps we used independence between A, B and C and proposition from textbook. 3. Two hunters shoot at a deer, which is hit by exactly one bullet. If the first hunter hits targets with probability 0.3 and the second with probability 0.6, what is the probability the second hunter killed the deer? The answer is not 2/3....
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This homework help was uploaded on 02/12/2008 for the course MATH 151 taught by Professor Liu during the Winter '08 term at Stanford.
 Winter '08
 Liu
 Math, Probability

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