If loga 10 23026 and loga 8 20794 estimate the following log

If loga (10) 2.3026 and loga (8) 2.0794, estimate the following: log a (640), log a (6.4)

loga(10) = 2.3026

loga(8) = 2.0794

a) loga(640) = loga(64*10)

= loga(8^2*10)

= 2loga(8) +loga(10) = 2*2.0794 + 2.3026

=6.4614

b) loga(6.4) = loga(64/10)

= loga64 - loga10

= 2loga8 -loga10

= 2*2.0794 - 2.3026

= 1.8562