Or do I nee a special ticket? I am using the paris museum pass as my entry. If anyone knows, I'd appreciate it if someone posted back!
CDG is in zone 5.
You need a specific RER ticket for Versailles. Buy one at the ticket booth in the Metro/RER station.
Any RATP ticket or pass valid for Metro zones 1-4 will get you to Versailles. Just take RER Line C, direction Versailles Rive Gauche.
A ticket from a carnet is good in zones 1-2. Versailles is in zone 4. The fare from central Paris to Versailles is €2.90 (each way). Be aware that the RER C line divides on the west side of Paris. Be sure to get on a train that is going to Versailles Rive Gauche.
Thank you for your help! what zone does charles de gaulle airport fit under?