<PRE><B>Question 439520</B>
log ( 2, 25 ) }}} and {{{ log ( 2, 3/5 ) }}} and {{{ log ( 2, 15 ) }}} and {{{ log ( 2, 75 ) }}} 
-------------
There is a Law of Logs called the change of base law.
It says: loga(b) = logc(b)/logc(a)
where c is any base you care to use.
-----------------------------------------
Your problem:
log2(25) = log(25)/log(2) = 1.3979/0.3010 = 4.644
================
Using your calculator:
log2(3/5) = log(3/5)/log(2) = -0.7370
---
log2(75) = log(75)/log(2) = 6.2288
=======================================
Cheers,
Stan H. 
</PRE>