90% of a radioactive sample is left undecayed
after a time 't' has elapsed. What percentage
of the initial sample will decay in a total time
2t.
1) 20%
2) 19 %
3) 40%
4) 38 %
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Answer:
Given that 90% is left un-decayed after time 't'.
Hence, 10% decays in time 't'.
Initially assume that the amount of substance is 'x'
After time 't' 10% is decayed.
i.e. Amount of substance left =0.9x
After further time 't' another 10% is decayed.
i.e. 0.1×0.9x is decayed
Leaving behind 0.81x.
Hence after time 2t we see that 0.19x has decayed, which is 19%.
Explanation:
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