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Stand by for another of Dave’s Dodgy Descriptions for you to blow holes in.  I just thought of this during my evening three miles constitutional
 
The Bar Technique in Logarithms

The magic thing about logs is that a plus or a minus in logs equates to a multiplication or division outside logarithms.  That means you can loan a number of powers of 10 (in the case of logs to the base 10) to a single term to complete a calculation with logs without transgressing the laws of algebra.  You do have to take it back again later of course to get the correct answer.

E.g. 3000x0.02 causes a problem in logs base 10, because 0.02 is less than unity

However, 3000 x 0.02 is the same as 3000 x 100x0.02/100 or 3000 x 2/100

Writing this in logs this is log3000 + Log 2 – Log 100 = 3.4771 + 0.3010 – 2.0000

However, that’s far too sensible, so let’s call it 3.4771 + bar2.3010 instead, bar2 in logs meaning the same as divided by 100 outside logs.  So stealling that bar2 back, the answer is antilog (3-2).7781= antilog 1.7781 which is 60. DaveP