# Science

A persistent organic pollutant is estimated to have a half-life of 30y. If 3 tonnes of the chemical exists in a polluted area today, how much of the chemical will remain after 120y.

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1. k = 0.693/t1/2
Substitute t1/2 and solve for k, then substiute into the equation below.
ln(No/N) = kt
No = 3
N = ?
k from above.
t = 120
Substitute and solve for N = tonnes remaining after 120 years

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