3. A radioactive substance has a rate of decay that can be modeled by the equations = ky, where k is a the value of k? constant and t is measured in years. If the half-life of the radioactive substance is 300 years, then what is 4. A population of fruit flies is increasing at an exponential rate. If on the 3rd day there were 400 fruit flies, and the 7th day there were 600 fruit flies, approximately how many flies were in the original population (day 0)