A radioactive isotope has a half-life of 20 days. If 100 gm of the substance is taken, the weight of the isotope remaining after 40 days is [NCERT 1979]

A radioactive isotope has a half-life of 20 days. If 100 gm of the sub

1.	A radioactive isotope has a half-life of 20 days. If 100 gm of the substance is taken, the weight of the isotope remaining after 40 days is [NCERT 1979]
A.	25 gm
B.	2.5 gm
C.	60 gm
D.	40 gm
Answer» B. 2.5 gm

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A radioactive isotope has a half-life of 20 days. If 100 gm of the substance is taken, the weight of the isotope remaining after 40 days is [NCERT 1979]

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