radiometric dating analysis on four igneous rocks uncovered

radiometric dating analysis on four igneous rocks uncovered at several sites that you have been exploring.
From the % lead you determine in each case, what is the appropriate age of the rock?

Rock A: 75% lead. Age of the rock __________________

Rock B: 50% lead. Age of the rock __________________

Rock C: 30% lead. Age of the rock __________________

Rock D: 10% lead. Age of the rock __________________

Solution

Rock A has 75% of lead that means 75% lead and 25% uranium. So it has undergone two half life decay. The half-life of Uranium 235 is 704 million years. so the age of the rock will be 2*704 which will equal to 1408 billion years.

Rock B has 50% of lead which means it has 50% lead and 50% Uranum and has undergone one half-life decay so it will have an age of 704 million years.

Rock C has 30% of lead which means it has 30% of lead and 70% of Uranium. Since the rock has not undergone a half-life decay it is difficult to estimate the age. But it will be near to one-half life of Uranium that is 704 million years.

Rock D has 10% of lead which means it has 10% of lead and 90% of Uranium. In this case, the disintegration has started and as it is said zero half life then the age of the rock is zero years. so the age will be zero years for the rock.