optimalisation by removing duplicate float() conversion

for these divisions we are sure that one side of the equation is already a
floating point number.

benchmark shows this can double performance for the division:

In [20]: %timeit 123/1.2
10000000 loops, best of 3: 77.1 ns per loop

In [21]: %timeit float(123)/1.2
10000000 loops, best of 3: 189 ns per loop
remove variable assignment for variable which is only used once (micro optimalisation)