Math w/o Calculator :
Log value for 60+ something.
Log 63 = 80 remember this one.
Next for every +3, add +2 for log value
Likewise log 60 = 58, we subtracted 2 against less 3.
And log 69 = 84.
And for 20+ s.
Log 20 = 30 remember this one.
And then for every +1 on 20, add double the amount with 30.
As such, log 25 = 20 + 5*2 = 30.
That covers everything except log 10s.