uations /inequalities. If you are stuck, use a graph " examples; this may help you find some clues. 19. (Modelling using exponential or logarithm functions) Most radioactive element illustrate a trait of exponential decay: its mass is lost while emitting radio waves. One of the radioactive isotopes of the element Californiam, Cu-250, has a half life of 13 years. How long will it take 1000 grams of Cu-250 to decay to 50 grams? // Note 1: Half-life is the time elapsed that the mass reduced to half of its initial value. // Note 2: You may use m=moe Where t is the year elapsed, m is the mass after the t years, and m, is the initial mass. If using this formulae, then you have to decide y from given conditions. Feel free if you want to use other methods and/or any other set of formulae