Final answer:
The amount A of Bismuth-210 after t days is given by the exponential decay formula A = 150 × 0.87^t, representing a 13% daily decay rate from an initial mass of 150 mg.
Step-by-step explanation:
The amount A of Bismuth-210 after t days can be represented using an exponential decay formula. Since the isotope decays by about 13% each day, this means that it retains 87% (or 0.87 times) its amount from the previous day. The formula for the remaining mass of Bismuth-210 after t days, starting with an initial mass of 150 mg, is given by A = 150 × 0.87^t.