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A radioactive substance takes 20 min to ...

A radioactive substance takes 20 min to decay 25%. How much time will be taken to decay 75% :

A

96.4 min

B

68 min

C

964 min

D

680 min

Text Solution

Verified by Experts

The correct Answer is:
A
For 25% decay
`K = (2.303)/(20) "log"(100)/(75) = (2.303)/(20) xx 0.1249 = 0.1438`
For 75% decay
`t = (2.303)/(0.01438) "log" (100)/(25) = 96.4` minute
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