maths

The half-life of lead is 22 years. How long will it take for a sample of this substance to

decay to 80% of its original amount

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  1. A = Ao * (1/2)^(n/22)

    .8 = .5^(n/22)

    log .8 = (n/22) log .5

    n/22 = .3219

    n =7.08 years

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