I was on a bus tour in Europe with the family. It officially ended in Paris. They gave us the option to pay a wad of extra money for them to take us to Versailles and Mont Martre on the bus.

We opted out of the additional tours. I bought Metro tickets for myself and the fam. We got to Versailles at about the same time that the rest of our tour group did. When we were finished at Versailles we hopped back on the Metro and arrived at Mont Martre way ahead of them.