The half-life of the decay of radioactive cesium(134) has been reported to be 2.062 years. What fraction of the original radioactivity will remain after 67 months?
#"Beginning Amount"#is the whole sample (here, #100%#) #n = "elapsed time"/"half-life"#
OR, more simply:
As a final note, "original radioactivity" probably isn't the most accurate wording, since radioactivity is a property and would suggest that a single atom of cesium-134 would change how likely it is to decay over time. A better choice of words would be "original sample of radioactive cesium-134."