If a radioactive nuclide has a half-life of 1.3 billion years, and it is determined that a rock contains 50% of its original amount of this nuclide, about how old is the rock?

Age of rock is 1.3 billion years

Explanation:

The half life of radioactive nuclide is 1.3 billion years

let us say that the original quantity of rock once upon a time would have been 100%

Half life period means the period in which the quantity of radioactive substance with in the nuclide reduces to half its original value.

Thus, time taken by nuclide to reduce to 50% of its original amount (i.e 100%, once upon a time) is 1.3 billion years.

Hence, it can be concluded that the time at which the nuclide has exactly 100% of its original amount would be 1.3 billion years.

Thus, the age of rock is 1.3 billion years.