>>>>That's my daughter's math question. I couldn't solve that... :(
>>>>
>>>>f(x/y)=f(x)+f(y)
>>>>f(10)=1
>>>>f(10000)=?
>>>
>>>Obviously the idea is to find out what the function is. The form of the function reminds me strongly of a logarithm (log ab = log a + log b), except that we have a division here. Are you sure the first part is plus, and not minus?
>>
>>why
>>
>>F(y)= -1*log(y )
>>
>>will do
>>
>>::)
>
>Experimenting a bit, I thought about that too, but in this case, f(10) would be -1, not 1.

F(x/y) = log(x/y)
F(x) = log(x)
F(y) = -log(y)

e.g.
log(x/y) = log(x)+(-log(y)) = log(x)-log(y)

x=100
y=10

(for each y=x*10)

log(x/y)=log(10)=1
log(10000) = 4

works perfect.