16. A sample of radioactive iodine-131 atoms has a half-life of about 8 days.

Suppose that 1 000 000 iodine-131 atoms are initially present.

a) Determine a formula for the number of atoms at time t, where t represents number of days

{2}

b) How long will it take for the sample to reach 180 000 atoms? Answer correct to 2

decimals. {3}