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Two radioactive materials A and B have decay constants 10 λ and λ , respectively. If initially they have the same number of nuclei, then the ratio of the number of nuclei of A to that of B will be 1/e after a time

1. λ 10 1
2. λ 10 11
3. λ 9 1
4. λ 11 1

Correct answer: λ 9 1

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