Question

A fossil bone has 25% of this new radioactive element remaining. If the half-life of this new element is 10,000 years, how old is the fossil bone?

Answer 1

the element starts off as 100%. half of 100% is 50% and half of 50% is 25%. the element has emitted 2 times the half life which is 10,000 x 2 = 20,000

the fossil bone is 20,000 years old