half life of element x

Question

Element X has a​ half-life of  7 days.  If we currently have a 26 ounce sample of Element​ X, how long will it be until only 3 ounces​ remain?ROUND YOUR ANSWER TO 2 DECIMAL

PLACES.

After about

enter your response here

​days, only 3 ounces will remain.

Answer 1

m(t) = m₀e^kt; m(7) = m₀e^7k = m₀/2; e^7k = 1/2; k = - ln2/7; m(t) = 26e^{- (ln2/7)t} = 3; 2^{- t/7} = 3/26;

t = - 7ln(3/26)/ln2 = 21.8 days