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Two radioactive substances A and B have decay constants 5 λ and λ respectively. At t = 0, a sample has the same number of the two nuclei. The time taken for the ratio of the number of nuclei to become 2 e 1 ⎟ ⎠ ⎞ ⎜ ⎝ ⎛ will be :

1. λ 2
2. λ 4 1
3. λ 2 1
4. λ 1

Correct answer: λ 2 1

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