# quick math question

**URL:** <https://boards.straightdope.com/t/quick-math-question/139386>\
**Category:** Factual Questions\
**Created:** [November 28, 2002, 7:48pm UTC](https://boards.straightdope.com/t/quick-math-question/139386 "2002-11-28T19:48:04Z")\
**Posts on this page:** 5\
**Page:** 1

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**Author:** ![rookie523](https://avatars.discourse-cdn.com/v4/letter/r/71c47a/32.png) [@rookie523](https://boards.straightdope.com/u/rookie523)\
**Post date:** [November 28, 2002, 7:48pm UTC](https://boards.straightdope.com/t/quick-math-question/139386/1 "2002-11-28T19:48:04Z")

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how do i isolate t?

(1.065)^t = 1000/875

thanks!

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**Author:** ![Balduran](https://avatars.discourse-cdn.com/v4/letter/b/cc9497/32.png) [@Balduran](https://boards.straightdope.com/u/Balduran)\
**Post date:** [November 28, 2002, 7:57pm UTC](https://boards.straightdope.com/t/quick-math-question/139386/2 "2002-11-28T19:57:56Z")

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Look at the trick of rewriting it in terms of exponentials and logarithms in your textbook.

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**Author:** ![John\_Kentzel-Griffin](https://avatars.discourse-cdn.com/v4/letter/j/ccd318/32.png) [@John\_Kentzel-Griffin](https://boards.straightdope.com/u/John_Kentzel-Griffin)\
**Post date:** [November 28, 2002, 8:00pm UTC](https://boards.straightdope.com/t/quick-math-question/139386/3 "2002-11-28T20:00:24Z")

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Hint: log(a^b) = b \* log(a)

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<div class="post-metadata">

**Author:** ![rookie523](https://avatars.discourse-cdn.com/v4/letter/r/71c47a/32.png) [@rookie523](https://boards.straightdope.com/u/rookie523)\
**Post date:** [November 28, 2002, 8:04pm UTC](https://boards.straightdope.com/t/quick-math-question/139386/4 "2002-11-28T20:04:07Z")

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it’s not a school question or homework.  
actually i’m working and a coworker asked me…

i found a formula on the net…

ln(1.065^t) = ln(1000/875)

etc.

thanks though!

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**Author:** ![mrcrow](https://avatars.discourse-cdn.com/v4/letter/m/838e76/32.png) [@mrcrow](https://boards.straightdope.com/u/mrcrow)\
**Post date:** [November 28, 2002, 8:19pm UTC](https://boards.straightdope.com/t/quick-math-question/139386/5 "2002-11-28T20:19:56Z")

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t=log (1000/875)/log 1.065  
they dont need to be natural logs…any will do  
=2.120394102 approx:)