If x and y are real numbers such that 4^x=27 and 9^y=16, what is the value of xy?
4x = 27 log both sides
x log 4 = log27
x = log 27 / log4 similarly 9y = 16 yields y = log 16 /log 9
xy becomes (log 27 log16) / (log4 log9) = 3
+36916 
