2. The half-life of a substance is defined as the period of time it takes for the amount of the substance to decay by half. The sequence below shows the amount of a substance that will be left after a certain number of half-lives have elapsed.
1, 1/2, 1/4, 1/8, . . .

b. Calculate how much of the substance will be left after 21 half-lives have elapsed. Show your work.
Does your answer make sense in this problem context? Why or why not?



Answer :