Math

the amount (in milligrams) of a drug in the body t hours after taking a pill is given by A(t)=30(0.8)t .
(a) What is the initial dose given?

(b) What percent of the drug leaves the body each hour?
Percent:

(c) What is the amount of drug left after 9 hours?

(d) What is the first whole number of hours at which there is less than 5 milligrams left in the body?

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  1. (a) at t=0, .8^0 = 1

    (b) .8 means decrease of 20%

    (c) 30*.8^9 = ?

    (d) 30*.8^t = 5
    .8^t = 1/6
    t log(.8) = log(1/6)
    t = log(1/6)/log(.8) = 8.03

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