Inaccuracy of decimal in .NET

By adding brackets you are making sure that the division is calculated before the multiplication. This subtlely looks to be enough to affect the calculation enough to introduce a floating precision issue.

Since computers can't actually produce every possible number, you should make sure you factor this into your calculations

Decimal can only store exactly values that are exactly representable in decimal within its precision limit. Here 22/24 = 0.91666666666666666666666... which needs infinite precision or a rational type to store, and it does not equal to 22/24 after rounding anymore.

If you do the multiplication first then all the values are exactly representable, hence the result you see.

decimal is not a magical do all the maths for me type. It's still a floating point number - the main difference from float is that it's a decimal floating point number, rather than binary. So you can easily represent 0.3 as a decimal (it's impossible as a finite binary number), but you don't have infinite precision.

This makes it work much closer to a human doing the same calculations, but you still have to imagine someone doing each operation individually. It's specifically designed for financial calculations, where you don't do the kind of thing you do in Maths - you simply go step by step, rounding each result according to pretty specific rules.

In fact, for many cases, decimal might work much worse than float (or better, double). This is because decimal doesn't do any automatic rounding at all. Doing the same with double gives you 22 as expected, because it's automatically assumed that the difference doesn't matter - in decimal, it does - that's one of the important points about decimal. You can emulate this by inserting manual Math.Rounds, of course, but it doesn't make much sense.