SOLUTION: If 10g of a radioactive substance are present initially and 9yr later only 5 remain, how much of the substance will be present after 18 yr?

Algebra ->  Logarithm Solvers, Trainers and Word Problems -> SOLUTION: If 10g of a radioactive substance are present initially and 9yr later only 5 remain, how much of the substance will be present after 18 yr?      Log On

From the condition, the half-life period is 9 years.


Hence, after 18 years since the starting moment, the remaining amount will be half of 5 grams, i.e. 2.5 grams.   ANSWER