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Home > A2C > Chapter 7 > Lesson 7.2.4 > Problem 7-146


The half-life of an isotope is 1000 years. A -gram sample of the isotope is sealed in a box.

  1. How much is left after 10,000 years?

    Half-life means time in which half of the original grams will remain.

    a is the initial value,
    b is the multiplier ( since we are working with a half-life),
    n is the number of thousands of years, and
    y is the amount of the isotope that remains (in grams).

    The equation is . Substitute for .

    Use the equation below, where x is the number of years.

  2. How long will it take to reduce to of the original amount?

    Use the equation from the help for part (a).
    In this case, of and you are solving for x.

  3. How long will it take until all of the original sample of the isotope is gone? Support your answer.