Question

An igneous rock contains one half of its original amount of K(potassium)-40. how old is the rock

Answer 1

Answer: the rock will
be 1.251 billion years old.

Hope this helps! ^^

Answer 2

Answer: 1.251 billion years

Explanation: 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.