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Eternal Intern
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In a certain animal population, for each of the first 3 [#permalink]
 07 Jun 2003, 13:06
. In a certain animal population, for each of the first 3 months of life, the probability that an animal will die during that month is . For a group of 200 newborn members of the population, approximately how many would be expected to survive the first 3 months of life?
(A) 140
(B) 146
(C) 152
(D) 162
(E) 170
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Manager
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dude, plz complete the first sentence
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Eternal Intern
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In a certain animal population, for each of the first 3 months of life, the probability that an animal will die during that month is 1/10 . For a group of 200 newborn members of the population, approximately how many would be expected to survive the first 3 months of life?
Sorry everybody, Uncle Stoylar, its time to take alook!
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Manager
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Month 1 : Dead = 1/10*200 =20
Month 2 : Dead = 1/10*(200-20)=18
Month 3 : Dead = 1/10*(200-20-18)=16
Total Dead = 54 => Alive = 200-54=146
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Eternal Intern
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It's really alot easier than I thought. Every chance they have is a probability question and is very similar like the official guide states.
9/10, 9/10 the 2nd, and 9/10 the third time.
Independent events, baby 
ETS works in patterns, exploit it.
But, if your like Tzolin, you got it baby!
thanks 
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Curly05 wrote: It's really alot easier than I thought. Every chance they have is a probability question and is very similar like the official guide states. 9/10, 9/10 the 2nd, and 9/10 the third time. Independent events, baby ETS works in patterns, exploit it. But, if your like Tzolin, you got it baby! thanks They probably work in patterns, but I would not put all my hope into that. 
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First month: 9/10*200 = 180 will survive
Second month: 9/10*180 = 162 will survive
Third month: 9/10*162 = 146 will survive
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The question is, how many would be expected to survive the 3 months?
The probability for survival each month is 9/10; thus, the probability for surviving 3 months is:
9/10 * 9/10 * 9/10 = 9^3/10^3
Multiply that with the original population of 200 and you get approx. 146.
Answer (B)
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close
