Question

1) Assume a substance is reduced by 24% in 32 hours. What is the substance's half-life in hours? 2) In the early 1960s, radioactive strontium-90 was released during atmospheric testing of nuclear weapons and entered the bones of people alive at the time. If the half-life of strontium-90 is 30 years, what fraction of the strontium-90 absorbed in 1961 remained in people's bones in 1996? 3) The population of a region is growing exponentially. There were 40 million people in 1980 (when t=0) and 65 million people in 1990. Find an exponential model for the population (in millions of people) at any time t, in years after 1980. P(t) = What population do you predict for the year 2000? Predicted population (millions) in the year 2000 = What is the doubling time in years? Doubling time =

          1) Assume a substance is reduced by 24% in 32 hours. What is the substance's half-life in hours?
2) In the early 1960s, radioactive strontium-90 was released during atmospheric testing of nuclear weapons and entered the bones of people alive at the time. If the half-life of strontium-90 is 30 years, what fraction of the strontium-90 absorbed in 1961 remained in people's bones in 1996?
3) The population of a region is growing exponentially. There were 40 million people in 1980 (when t=0) and 65 million people in 1990. Find an exponential model for the population (in millions of people) at any time t, in years after 1980.
P(t) =
What population do you predict for the year 2000?
Predicted population (millions) in the year 2000 =
What is the doubling time in years?
Doubling time =

Added by Michelle V.

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