Question 4 and 5 - no need for long explanation

4- A radioactive Sample with an initial mass of 25 ng has a half-life of 2 days . a ) write an equation to model this exponential decay what is the time, in days, and A is the amount of the substance that remains. b) what is the amount of radioactive material remaining after 7 days? 5- The population of a city is growing at an average rate of 3% per year. In 1990 , The population was 45,000. a) write an equation that models the growth of the city b ) use the equation to determine the population of thecity in 2007. () Determine the year during which the population will have doubled