What is the minimum number of doctors that could be at Souderton?

Luke February 26, 2020

Rule 2 & 4 contradiction?

Ive diagramed rule 2 Jr > Os and rule 4 Nr > Or I don't see any reason why J and N couldn't both be in R at same time which would mean both Os & Or which isn't possible. What am I missing?

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SamA February 26, 2020

Hello @Luke,

Remember that these rules are conditional. The sufficient condition doesn't have to occur. But if it does, we know that the necessary condition will follow.

2. "Onawa is at Souderton IF Juarez is at Randsborough."
Jr - - - -> Os
4. "IF Nance is at Randsborough, then so is Onawa."
Nr - - - -> Or

The fact that O cannot simultaneously be at Randsborough and Souderton is the reason why J and N cannot both be at Randsborough. Therefore, one of them has to be at Souderton. There is no problem here, you actually made an important inference.

It is ok that these rules conflict, because they are conditional! It doesn't say that J and N are definitely at R. It just tells us what happens when each of them are placed at R. You figured out that they cannot both be there.