The old age of rock when examined is 21.4 million years if the ratio of uranium-235 to lead-207 is found to be 125,000:875,000. the half-life of uranium-235 is 700 million years.
<h3>Decaying Equation </h3>
P = [P + D] (1/2) ^(t/t(1/2))
where,
P represent the present parent amount
D is the present daughter amount
t(1/2) is the half life time period
t is the actual age
We know that,
t = (log[(P+D) /P] / log2) × t(1/2) ----------(1)
Given,
P = 97.6
D = 2.1
Ratio of P and D can be calculated as
P/D = 97.6/2.1
= 46.476
By substituting all the values in eq(1), we get
t = [(log 46.476 +1)/log2] × t(1/2)
Given,
The half life of U —Pb decay is 700 million years.
So,
t = [(log 46.476 +1)/log2] × 700
t = 21.4 million years.
Thus, we calculated that the the old age of rock when examined is 21.4 million years.
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DISCLAIMER:
The given question is misprint on portal.
Here is the correct form of question:
A rock is examined to determine its age, and the ratio of uranium-235 to lead-207 is found to be 125,000:875,000. the half-life of uranium-235 is 700 million years.
How old is the rock if it contains Uranium-235/ lead-207 ratio of 97.6 to 2.1?
