Answer:
Age of rock = 500 million years
Explanation:
The age of the rock can be calculated by determining the number of decays (half-lives) the parent rock has undergone.
The half-life of a radioactive material is the time it takes for half the the quantity present in that material to decay or disintegrate.
The half-life of the rock sample = 250 million years
Amount of parent rock left in the rock sample = 25% = 1/4
Number of half-lives, n required is given as (1/2)ⁿ
Number of half-lives undergone by the parent rock sample to be 1/4 of the original sample is given as: (1/2)ⁿ = 1/4
1/4 = (1/2)²
Therefore, n = 2
Age of rock = number of half-lives * half-life (in years)
Age of rock = 2 * 250 million years
Age of rock = 500 million years
