G/S OUT + G/S HOME = TAS x 2
This is only true when the wind out is the same as the wind back.
If you're working out a PNR based on abnormal ops then your flight level home may be quite different to your flight level out. In that case the winds may be different and you need to use G/S OUT + G/S HOME instead of TAS x 2.
Distance to CP is the same formula except you use DISTANCE instead of time, and the answer is a distance.
CP = Total distance x GS HOME
........G/S OUT + G/S HOME
You may have noticed that these formulas are the same as for an exam. There is a reason they are in the exam!