The half-life of radium is about `1600 yr`. Of `100g` of radium existing now, `25 g` will remain unchanged after

Options

A. 2400 years
B. 3200 years
C. 4800 years
D. 6400 years

Answer

B

Explanation

Since, `(M)/(M_(0)) = ((1)/(2))^((t)/(T_(1//2))) rArr ((25)/(100)) = ((1)/(2))^((t)/(1600))`
`rArr 2= (t)/(1600) rArr t= 3200` years