1) If dairy cows eat hay containing too much iodine 131, their milk will be unfit to drink. suppose some hay contains 10 times the maximum allowable level of iodine 131. how many days should the hay be stored before it is fed to dairy cows? (iodine 131 is produced by nuclear explosions, but it presents less of a hazard because it has a half life of 8 days)

2) A certain wild animal preserve can support no more than 250 lowland gorillas. 25 were known to be in the preserve in 1970. In 1980, the population reached 58. if the growth is logistic, find the constants C,A, and k

1) 8 days is the time it takes half of the iodine to deteriorate. You need to reduce the content to 1/10. Thus, 90% needs to vanish. divide 10 by 2 3 times, and you reach 1.25. Remove 1/5, and you reach an allowable level. So, 3 periods of 8 days, +2/5 of one (1/5 is 2/5 of 1/2). We get 24+3.2=27.2 days for the iodine to become safe.

2). I'm not sure what C and A are, we've been focused on trig identities. I assume the growth is directly proportional with the time elapsed.

Filed under: dairy hay

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