What is the best and most inexpensive route from charles de gaulle to the city of paris near place monge?

Question

What is the best and most inexpensive route from charles de gaulle to the city of paris near place monge?

Answer 1

Rilifan is right . But you can also go from CDG to Luxembourg RER station  (direct ) . and then walk to Place monge . See on the Map centered on Place Monge ( click on + icon  to zoom )

Answer 2

AirFrance bus then either the metro or city bus

Answer 3

From CDG take the RER B commuter line makred "Direction : Massy-Palaiseau" to the Chatelet-Les Halles Station and change to Metro line 7 marked "Direction : Mairie d'Ivry" to the Place Monge (Jardin des Plantes) stop.