Simplify fraction - Where did the rest go? While studying maths I encountered the following fraction :
$\frac{5ab}{10b}$
Which I then had to simplify. The answer I came up with is:
$\frac{5ab}{10b} = \frac{ab}{2b}$
But the correct answer seemed to be:
$\frac{5ab}{10b} = \frac{a}{2} = \frac{1}{2}$a
Why is the above answer correct and mine wrong? I can't wrap my head around $b$ just disappearing like that.

If you are OK with cancelling the factors of 5 in the numerator and the denominator, well, this is just cancelling the factors of $b$ in the numerator and denominator. 
