A radioactive isotope has a half-life of 10 day. If today there are 125 g of left, what was the original mass 40 day earlier? a)600 g b)1000 g c)1250 g d)2000 g

Options

A. 2000g
B. 600 mg
C. 1 g
D. 1.5 g

Answer

A

Explanation

`N = N_(0) ((1)/(2))^(n) .n = (40)/(10) = 4`
`(125)/(1000) = N_(0) ((1)/(2))^(4), N_(0) = (125)/(1000) xx 2 xx 2 xx 2 xx 2 = 2g`