If the half-life of the pesticide is 12 years
what fraction of the pesticide will be left after 36 years? 100 years?
how many years will it take fir for 99.9% of the pesticide to decompose?

K = 0.058 yr (constant)

Fraction of the pesticide  = 36 years/12 = 3 half-lives   , so around 1/8 left

when 99.9 % decomposed, 0.1 % is left , so the fraction is 0.001. To reach this point, it will take around +/- 120 years

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