[Resolved] Easy Question, The Sequel

Okay, I'm presented with this problem:

Quote:

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The half-life of element X is 9 hours. If 80mg are present now, how much will exist after 2 days?

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So I used the formula A(t) = A0 * e ^ kt

Code:

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.5 = e ^ 9k
ln .5 = 9k
k = ln (.5)/9
k = -0.0077

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So now I have A(t) = A0 * e ^ -.0077t

So I do:

Code:

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A = 80e ^ -.0077(48)
A = 3810.55

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Which obviously isn't correct. What am I doing wrong?

Nevermind.

I forgot to put these parenthesis:

Code:

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A = 80e ^ (-.0077(48))

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hmm...that gives me 55.28, which still doesn't seem right. Any ideas?

Quote:

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k = -0.0077

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-0.0770

Quote:

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Originally posted by kedaman
-0.0770

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Bah. Thanks kedaman :)

'twas an optical illusion ;) ..waaaah.. liquidgeneration sabotage!