Iridium is a radioactive element used for therapy in nuclear medicine. It decays to ½ or 2-1, of its original mass after 74 days. After 148 days, it decays to ¼, or 2-2, of its original mass.  What fraction remains after 222 days? Write fraction as a power of 2 with a negative exponent also. What fraction remains after 370 days? Write fraction as a power of 2 with a negative exponent also.

Iridium is a radioactive element used for therapy in nuclear medicine. It decays to ½ or 2^-1, of its original mass after 74 days. After 148 days, it decays to ¼, or 2^-2, of its original mass.

1.  What fraction remains after 222 days? Write fraction as a power of 2 with a negative exponent also.
2. What fraction remains after 370 days? Write fraction as a power of 2 with a negative exponent also.