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September 23rd, 2015, 07:43 AM   #1
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Simple question

Given that k = ln 50/60 and A = 10/60

The given equation is A = e^(kt)
1)
10/60 = e^(kt)
ln 10/60 = kt
t = (ln 10/60 ) / ln (50/60) = 9.827

2)
10/60 = e^ (ln (50/60)t)
10/60 = 50/60 t
t = 0.2

Why do I get 2 different answers? Did I do anything wrong?

Last edited by skipjack; September 23rd, 2015 at 07:09 PM.
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September 23rd, 2015, 07:54 AM   #2
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Quote:
Originally Posted by KaiL View Post
Given that k = ln 50/60 and A = 10/60

The given equation is A = e^(kt)
1)
10/60 = e^(kt)
ln 10/60 = kt
t = (ln 10/60 ) / ln (50/60) = 9.827

2)
10/60 = e^ (ln (50/60)t)
10/60 = 50/60 t
t = 0.2

Why do I get 2 different answers? Did I do anything wrong?
Your second answer is wrong because you treated it as ln((50/60)t) rather than ln(50/60) times t.

Last edited by skipjack; September 23rd, 2015 at 07:10 PM.
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September 23rd, 2015, 08:03 AM   #3
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Quote:
Originally Posted by Country Boy View Post
Your second answer is wrong because you treated it as ln((50/60)t) rather than ln(50/60) times t.
Oh I see. Thanks for correcting my mistake.

Last edited by skipjack; September 23rd, 2015 at 07:10 PM.
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