Question

Possible Duplicate:
Is JavaScript's Math broken?

It returns

5.074999999999999

Why is that?

And what other numbers will give a similar demonstration of this?

Answer 1

Essential reading on floating point arithmetic.

http://docs.oracle.com/cd/E19957-01/806-3568/ncg_goldberg.html

In a nutshell:

Squeezing infinitely many real numbers into a finite number of bits
requires an approximate representation. Although there are infinitely
many integers, in most programs the result of integer computations can
be stored in 32 bits. In contrast, given any fixed number of bits,
most calculations with real numbers will produce quantities that
cannot be exactly represented using that many bits. Therefore the
result of a floating-point calculation must often be rounded in order
to fit back into its finite representation. This rounding error is the
characteristic feature of floating-point computation.