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Gmat paper test - combined areas

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Gmat paper test - combined areas

by tanyajoseph » Wed Sep 19, 2007 2:41 pm
In a certain animal population, for each of the first three 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?
a) 140
b) 146
c) 152
d) 162
e) 170

OA after few attempts.
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by karthick451 » Wed Sep 19, 2007 5:09 pm
answer is B

1 in 10 will die.

20 in 200 after 1st month
18 in 180 after 2nd month
approximately 16 in 162 after 3 months

final number left will be 146
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by kajcha » Wed Sep 19, 2007 5:54 pm
B for me
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by samirpandeyit62 » Wed Sep 19, 2007 9:43 pm
given probabity than an animal dies is 1/10 for each of the first three months

so P (animal surivies) =9/10 for each of the 3 months

so P (animal survives all the 3 months) =(9/10)^3

so nos of animals that survive 3 months = (9/10)^3 *200 = 146 approx

so ans B
Regards
Samir
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