Answer:
Volume
Explanation:
In chemistry, the CONCENTRATION of a solution is the amount of a substance present within a volume of another substance. In other words, the concentration refers to the amount of a solute dissolved in a particular volume of a solvent to make a solution.
Concentration can be expressed in mass per volume i.e. g/cm³ or mol per volume i.e. mol/L or mol/dm³ etc. The amount of a substance is measured in Mass or mole, while the volume of a substance in Litres (L).
Answer:
2.6 billion years old
Explanation:
Initial:
100% k-40
0% ar-40
After 1.3 billion years:
50% k-40
50% ar-40
After 2.6 billion years:
25% k-40
75% ar-40
So the rock is 2.6 billion years old.
