The half-life of a radioactive isotope ‘X’ is 20 years. It decays to another element ‘Y’ which is stable. The two elements ‘X’ and ‘Y’ were found to be in the ratio 1 : 7 in a sample of a given rock. The age of the rock is estimated to be -
A
40 years
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B
60 years
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C
80 years
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D
100 years
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Solution
The correct option is B 60 years Half-life of X ⇒TX = 20 years