#1

I just started with logarithms, and I'm pretty clueless about them. So here's one of the questions I have, and if you can explain it, I'll probably be able to figure out the rest.

NB: all the bases for these questions are x

If log 3 = 1.5, log 5 = 1.8 and log 10 = 3.0 :

evaluate log 15

thanks in advance

NB: all the bases for these questions are x

If log 3 = 1.5, log 5 = 1.8 and log 10 = 3.0 :

evaluate log 15

thanks in advance

#2

which base are you using

#3

in the book, the base just says x

edit: ya liek I said I'm pretty much clueless about all this

edit: ya liek I said I'm pretty much clueless about all this

#4

log 15 should be log 3 times 5

Edit: but ive got no idea im going off logic

Edit: but ive got no idea im going off logic

#5

cant exactly remember but i think when you multiply logs you add wat their value is together

so log3 x log 5 = 1.5 + 1.8

not exactly sure tell me if its wrong ill actually get the book out

so log3 x log 5 = 1.5 + 1.8

not exactly sure tell me if its wrong ill actually get the book out

#6

the answer for that Q is meant to be 3.3, but I don't know how to get it

edit: and ur answer is correct, cheers

edit: and ur answer is correct, cheers

#7

if log_a b = c

then a^c = b

log_x 3 = 1.5

x^1.5 = 3

x =3^(1/1.5) =3^(2/3)

and so on for the others

if you need to work out what the base is

then a^c = b

log_x 3 = 1.5

x^1.5 = 3

x =3^(1/1.5) =3^(2/3)

and so on for the others

if you need to work out what the base is

#8

log15 = log(3x5) = log3 +log5

One rule of logarithms is:

log(ab) = loga +logb

The handiness of this is that what was a multiplication problem has become an addition problem.

A few others:

log(a/b) = loga - logb

log(a^r) = r x loga

That's probably all you need.

One rule of logarithms is:

log(ab) = loga +logb

The handiness of this is that what was a multiplication problem has become an addition problem.

A few others:

log(a/b) = loga - logb

log(a^r) = r x loga

That's probably all you need.

#9

cheers for all your help people, I'll post if I need more help

Thanks

Thanks