How to memorize common logarithms

index  multiplier  log

2   * .15 =   .3

3  * .16 =  .48

4 * .15 = .60

5 *.14  = .70

6* .13 = .78

7 * .12 = .84

8 * .11 = .88

10 * .10 = 1.0

and 9 is half way from .9 to 1.0, so .95

Comparison to more exact values

2   * .15 =   .3  v .301

3  * .16 =  .48 v .477

4 * .15 = .60 v .602

5 *.14  = .70 v .698

6* .13 = .78 v .778

7 * .12 = .84 v .845

8 * .11 = .88 v .903

9 * .105 = .945 v .954

10 * .10 = 1.0 v 1.0

=

2,3,4,5,6,7,8

15,16,15,14,13,12,11

Then remember that 10 has a log of 1, so it is 10 in above list.

2,3,4,5,6,7,8,10

15,16,15,14,13,12,11,10

Then 9 fits in between so it is 10.5.

You can remember this by 3 is 16, and count down by one in each direction.

Or remember that 10 is 10, skip 9 and count up by one from 8.  When you get to 3, remember to go back down when go to 2.

http://nerdparadise.com/math/tricks/base10logs/

Started by twitter conversation

https://twitter.com/centerofmath/status/240028475191336961

https://twitter.com/MarkTenneyNewMa/status/240043748288000000

Example of previous lesson in this line

http://www.curiousmath.com/index.php?name=News&file=article&sid=32

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About New Math Done Right

Author of Pre-Algebra New Math Done Right Peano Axioms. A below college level self study book on the Peano Axioms and proofs of the associative and commutative laws of addition. President of Mathematical Finance Company. Provides economic scenario generators to financial institutions.
This entry was posted in Common Logs 2 to 10, Math Memory Tricks. Bookmark the permalink.

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