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Math Help - Exp Function Word Problem

  1. #1
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    Exp Function Word Problem

    The probability, P, in percent, that a person will respond to a certain ad can be modelled by the equation P(n)=1-2^(-0.05n), where n is the number of days since the ad began on tv. After how many days is the probability greater than 20%?

    my work:
    0.20=1-2^(-0.05n)

    then i solved for n, but i got a negative number.. what is wrong with my equation that i made and why
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  2. #2
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    Quote Originally Posted by skeske1234 View Post
    The probability, P, in percent, that a person will respond to a certain ad can be modelled by the equation P(n)=1-2^(-0.05n), where n is the number of days since the ad began on tv. After how many days is the probability greater than 20%?

    my work:
    0.20=1-2^(-0.05n)

    then i solved for n, but i got a negative number.. what is wrong with my equation that i made and why
    Start by solving 1-2^{-0.05 n} > 0.20 \Rightarrow -2^{-0.05 n} > -0.80 \Rightarrow 2^{-0.05 n} < 0.80.

    If you want more details it would be best to post the details of how you solved your inequation.
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