A group of teenagers are washing cars to raise money for a charity. They will wash six cars today, one a time. The cars are a Ranger, a Stalwart, a Trek, a Voltaire, a Warbler, and a Zipper. The Trek is washed immediately before the Ranger or the Zipper. The Zipper is washed before the Stalwart and the Warbler. The Voltaire is washed immediately after either the Stalwart or the Warbler.
If the second car washed is the Ranger, when is the Zipper washed?
Only T, R, and Z can be washed first because S, W, and therefore V must come after Z. If R is second, then T must be first since the only other option is Z and that wouldn't allow for the TR or TZ rule. So, we have T, then R. The next car must be Z because S, W, and V all have to come after Z.