in a sample of rocks with concentration of both radioactive and stable in a given ratio,  how can we calculate the age of the rock,  assuming the rock was formed when time =0,

Then

OR ALTERNATIVE WE CAN DERIVE THE EQUATIONS AS FOLLLOWS

According to the  law of radioactivity, the rate of decay is proportional to the original number

Note replace H with λ

TAKING THE reciprocal from both side we have

 But let D =

                                                                        (1)Austrlian govt. geoscience

                                                                        (2)GeoExplo LTdaA