# Joint Entrance Examination/2000 Screening/Q022 Radioactive materials and decay constant

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# Original Question by Dharav talk

Here's the question...
 Two radioactive materials X1 and X2 have decay constants 10λ and λ? respectively. If initially they have the same number of nuciei, then the ratio of the number of nuclei of X1 to that of X2 will be 1/e after a time... (A) ?1/10λ (B) 1/11λ (C) 11/10λ (D) 1/9λPosted by Dharav talk 05:00, 18 August 2009 (UTC)

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