How do I find the approximate value of #log_5 100#?

1 Answer
Sep 1, 2014

Well, for starters, remember that logs are really just powers in reverse!
If you know some powers of 5, then just keep going...
#5^2=25# and #5^3=125# , so the answer must be between 2 and 3.
Use a scientific calculator (at least) to continue guessing:
My screenshot 5

However, some calculators will give you a much better answer, and much faster:
My screenshot 6

If you don't have this kind of option on your calculator, try some online: Online log calc