Each hour, on the hour, a bus leaves Duluth for St Paul and another bus leaves St Paul for Duluth. The trip takes 3 hours from Duluth to St Paul and 3 hours from St Paul to Duluth. How many buses will a bus leaving Duluth at noon meet on its way to St Paul?

I assume that before the bus leaves Duluth, there are already buses on the way to Duluth from St Paul.

If you make a simple sketch, you'll find that at noon, there are two buses from St Paul on their way to Duluth.

At 12.30, the bus meets with the first bus.
At 1.00, the bus meets with the second bus,
And so on.

Can you solve this now?