20 mg of C-14 has half-life of 5760 yr. 100 mg of sample containing C-14 is reduced to 25 mg in

Options

A. 11520 yr
B. 5760 yr
C. 18270 yr
D. 17280 yr

Answer

A

Explanation

`25=[(1)/(2)]^(n)xx100`
`[(1)/(2)]^(n)=(25)/(100)=(1)/(4)=[(1)/(2)]^(2)`
n=2
No. of half lives=2
so time required `=2xx5760`
=11520 yr