Three grams of Bismuth-218 decay to 0.375 grams in one hour. What is the half-life of this isotope?
igcse question

Explanation:

Use half life equation:

A = A₀ (½)^(t / T)

where A is the final amount,

A₀ is the initial amount,

t is time,

and T is half life.

0.375 = 3 (½)^(1 / T)

0.125 = (½)^(1 / T)

(½)^3 = (½)^(1 / T)

3 = 1 / T

T = 1/3 hours

T = 20 minutes

the answer would be c