If Nation Z exports tea and wheat, then which one of the following must be true?
Zienaon February 26, 2020
I thought "only if" introduces necessary conditions
Why can't Y have Soybeans without X? I thought necessary conditions can still exist without sufficient, and "only if" introduced necessary..
For example, why cant this be a solution:
X: R O
Y: S O
Z: T W
Reply
Irinaon February 27, 2020
@hatemz,
If and only if is bidirectional.
Nation X exports soybeans if, but only if, Nation Y does also.
We can break it down into two separate statements:
(1) If Y exports soybeans THEN X exports soybeans.
Y -> X
(2) ONLY IF Y exports soybeans THEN X exports soybeans.
X -> Y
~ Nation Y< - > ~ Nation X Nation X < -> Nation Y
meaning that either both X & Y export soybeans or neither one of them.
