# Age Calculation of a Rock Sample Containing Potassium-40

The half-life of potassium-40 is 1.25 billion years. This means that over time, half of the potassium-40 atoms in a rock sample will decay into other isotopes. To calculate the age of the rock, we can use the concept of radioactive decay. If the sample contains 6.14 × 10-4 g of Rb-87 and 3.51 × 10-5 g of Sr-87, we can determine the ratio of Rb-87 to Sr-87 to find the number of half-lives that have passed. Then, we can multiply the number of half-lives by the half-life of Rb-87 to find the age of the rock.

In this case, we can set up the following equation to calculate the age:

** Age of the rock = Number of half-lives * Half-life of Rb-87**

By substituting the values of Rb-87 and Sr-87 into the equation and calculating the ratio, we can determine the number of half-lives that have passed. Once we have this information, we can multiply it by the half-life of Rb-87 to find the age of the rock sample containing potassium-40.