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 A bacteria colony initially has mass g. After two hours, the colony has mass g. Find the mass after 5 hours. Find the time it takes for
the original mass of the colony to triple.
 A metal plate that has been heated cools from to
in 20 minutes when surrounded by air at a temperature of
. What will the temperature of the plate be be after one
hour of cooling? When will the temperature of the plate reach ?
 Just before midday the body of an apparent homicide victim is
found in a room that is kept at a constant temperature of . At 12 noon the temperature of the body is and at 1
P.M. it is . Assume that the temperature of the body at
the time of death was . What is the time of death?

 Radioactive radium has a halflife of approximately 1600
years. What percentage of a present amount remains after 100
years?
 If radioactive material decays continuously at a rate
proportional to the amount present, find the halflife of the
material if after one year, 99.57 % of an initial amount
still remains.
Roxanne Tisch
Tue Sep 24 13:59:38 EDT 1996