Why do simple math operations on floating point return unexpected (inaccurate) results in VB.Net and Python?

Question

x = 4.2 - 0.1  

vb.net gives 4.1000000000000005
python gives 4.1000000000000005

Excel gives 4.1<

Answer 1

There is no problem, really. It is just the way floats work (their internal binary representation). Anyway:

>>> from decimal import Decimal
>>> Decimal('4.2')-Decimal('0.1')
Decimal('4.1')