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Half-lives of two radioactive substances...

Half-lives of two radioactive substances `A` and `B` are respectively `20` minutes and `40` minutes. Initially, he sample of `A` and `B` have equal number of nuclei. After `80` minutes the ratio of the remaining number of `A` and `B` nuclei is :

A

`1:4`

B

`4:1`

C

`1:16`

D

`1:1`

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The correct Answer is:
A
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