Question

How much of a radioactive kind of promethium will be left after 20 days if you start with
9,056 grams and the half-life is 5 days?

Answer 1

in 20 days 4 half life will be completed

so n = 4

formula :-

$\frac{ A\degree}{ {2}^{n} } = \frac{9056}{ {2}^{4} } = \frac{9056}{16} = 566grams$