how to solve log questions

Question

turingtest · Answer

by using log properties

could you please post a specific question?

anonymous · Answer

which of the following is equivalent to log[4](7)

turingtest · Answer

you have not typed "the following" yet, but I'm betting that this is a case to apply the change of base formula$$\large\log_bx={\log_bx\over\log_ba}$$

anonymous · Answer

i dont understand how to do that

turingtest · Answer

like I say, that is just a guess
your question is obviously multiple choice, and in this case, since there are infinitely many ways to write this expression, we really do need the choices

anonymous · Answer

how bout this question: if an earthquake has a magnitude of 7.3 on richter scale how much energy is released(richter scale is (logE=5.24+1.44M)

turingtest · Answer

just plug in M it looks like

turingtest · Answer

you then get
logE=(some number)
which implies that 
E=10^(some number)

anonymous · Answer

choices are: A.1.6x10^2j B.5.6x10^15j C.1.8x10^29j D.5.8x10^48j

turingtest · Answer

that's nice, but I'm not going to give the answer away like that, and in this case since there is only one correct possible answer we don't need the multiple choices

turingtest · Answer

in any event, it is the aim of this site to teach, not just provide answers, so please don't look for that

turingtest · Answer

the formula is$$\log E=5.24+1.44M$$first plug in M, what do you get?

anonymous · Answer

15.752

turingtest · Answer

so we have$$\log E=15.752$$what is the inverse operation of the logarithm?