Question

7. Arrival of the Normandy Train

Claude is waiting to meet the train from Normandy at Gare Saint-Lazare in Paris. He
tells Marie the hour of the train's arrival and he tells Jean at which minute it arrives. He
also tells them both that the train arrives between 0600 and 1000.
They consult the timetable and find the following services between those times:
0620, 0639, 0650; 0717, 0746; 0825, 0839; 0917, 0925, 0950.
Marie then says, “I don't know when Claude's train arrives, but I'm sure that neither does
Jean."
Jean replies, “I didn't know his train, but now I do."
Marie responds, “Now I do as well!"
When is Claude's train and how do you know?

Answer 1

The train is 0839

Explanation:

First off, 0620 and 0746 are not available options, as Jean would've immediately know, as they're the only one with non-repeated minutes.

Now, when Marie says "I'm sure neither does Jean", it means she didn't get 06 or 07, as those are the number that has 0620 and 0746, which then she cannot ensure that Jean doesn't know the train arrival.

We're left with 0825, 0839, 0917, 0925 and 0950

After that, Jean said he knows the train number. So, he couldnt've gotten 25, as it is repeated in the 5 options we pick. => we're left with 0839, 0917 and 0950.

And then, Marie responds now she does as well, which it cannot be 09, as it is repeated.

So, the train number is 0839.