Answer :
Answer:
Hence, the age of rock in which 25% of the original amount remain is:
10 million years.
Step-by-step explanation:
A radioactive substance has a half-life of 5 million years.
What is the age of a rock in which 25% of the original radioactive atoms remain?
Let x be the initial amount of the substance.
Hence, 25% of the initial amount is:
x/4
i.e. in the table form the age could be represented as:
Years Amount left
5 million years x/2
10 million years x/4.
Hence, the age of rock in which 25% of the original amount remain is:
10 million years.