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# Intro to logarithms

Sal explains what logarithms are and gives a few examples of finding logarithms. Created by Sal Khan.

## Want to join the conversation?

• Is log base 1 of 1 equal to 1, 0, or both?
• Log base 1 of 1 would have infinite answers not just 1 and 0
• Can a logarithm be written without a base?
• Writing a log without a base is implied that it has base 10.
log(100) = log_10(100) = 2

The other "exception" is the natural log, which you don't write with a base.
ln(x) is the same form as log_e(x), but ln is more perferred.
• what is the value of n if 0.28=1/(1.09)^n? using logarithm
• n=log_(1/1.09)=0.28 is the logarithmic form
• In what grade do you learn logarithims?
(1 vote)
• Hi! I learned it in Algebra 2, which normally people take in 10th grade. I took it in 9th grade.
• is there any synonym of logarithms?
• Yes! And explain how to use logarithms with decimals!
• Is the word 'base' used in a logarithm context with a different meaning than when one says that a number is written in base ten, base two, base five, etc.?
• The word base refers to its definition as used with exponents.
If you have 2^6
The "2" is the base and the "6" is the exponent.
"Log base 2 (64)" is asking you to find what exponent would you apply to the base "2" to create 64. Or... 2^( _ ) = 64. fill in the appropriate exponent.
Hope this helps.
• can you teach my divison?
• Start learning it with a times table. To multiply on a times table (such as 6*8) find there the six line meets the 8 line at 48. To divide 48/6, go on the 6 line until you find 48, then go up to 8. To divide 48/8, go on the 8 line until you find 48, then go up to 6. This should help get the idea of multiplication and division being opposite operations.