#log ab = log a + log b#

#log a/b = log a - log b#

#log a^b = b * log a#

#log 20 = log 4*5 = log 2*2*5#

#=> log 20 = log 2 + log 2 + log 5#

#=> log 20 = 0.301 + 0.301 + 0.699#

#=> log 20 = 1.301#

#log 2.5 = log (5/2)#

#=> log 2.5 = log 5 - log 2#

#=> log 2.5 = 0.699 - 0.301#

#=> log 2.5 = 0.398#

#log 125 = log 5^3 = 3 * log 5#

#=> log 125 = 3 * 0.699#

#=> log 125 = 2.097#