1. When a cold drink is taken from a refrigerator, its temperature is 5°C. After 25 minutes in a 20°C room its temperature has increased to 10°C. (Round your answers to two decimal places.)
(a) What is the temperature of the drink after 30 minutes?
(b) When will its temperature be -1°C?
2. The half-life of cesium-137 is 30 years. Suppose we have a 60-mg sample.
(a) Find the mass that remains after t years.
(b) How much of the sample remains after 110 years? (Round your answer to two decimal places.)
(c) After how long will only 1 mg remain? (Round your answer to one decimal place.)
3. A bacteria culture initially contains 100 cells and grows at a rate proportional to its size. After an hour the population has increased to 260.
(a) Find an expression for the number of bacteria after t hours.
(b) Find the number of bacteria after 4 hours. (Round your answer to the nearest whole number.)
(c) Find the rate of growth after 4 hours. (Round your answer to the nearest whole number.)
(d) When will the population reach 10,000? (Round your answer to one decimal place.)