If log 2=0.3010and log=0.6990.find log40

Answer 1

It is a good thing that I know enough about logs to correct your typo
and say log 5 = .6990

log 40 = log (8*5)
= log8 + log5
= log 2^3 + log 5
= 3log2 + log5
= 3(.3010) + .6990
= .9030 + .6990
= 1.6020

Answer 2

log40 = log4 + log10 = 2*0.310 + 1 = 1.6020