Question

An igneous rock contains one half of its original amount of potassium 40 the age of the igneous rock is closest to what

Answer 1

Answer:

$1.25\times 10^{9} years$

Explanation:

The half life of potassium 40 is $1.25\times 10^{9} years$.

The time taken by the substance to decay into its half the quantity is called half life.

So, the time taken by the potassium 40 to decay by half amount is one half life.

Thus, the life of the rock is $1.25\times 10^{9} years$.

Answer 2

So we want to know what is the age of igneous rock if it contains one half of its original amount of potassium 40. The half-life of potassium 40 is 1.251*10^9 years. Since in the igneous rock there is one half of potassium left it means only one half-life has passed. And its age is 1.251*10^9 years or 1.251 billion years.