If O is selected for the first Sunday, which one of the following is a concerto that must also be selected?

Anna on January 4, 2020

Can someone please explain this problem?

I don't see how you can infer that Y must be selected

2 Replies

Anna on January 4, 2020

*that K must be selected

Skylar on January 5, 2020

@AnnaC, happy to help.

We are told that O is selected for the first Sunday.

Rule #4 states: J and O -> J - O. The contrapositive of this is: O - J -> NOT J or NOT O.
Basically, this means that if both J and O are selected, J must precede O. If O would precede J, then they cannot both be selected. In this scenario, we know O is selected and is in spot 1, which means it would be impossible for J to be earlier than O. Therefore, J cannot be selected in this scenario.

The game setup tells us that exactly two of Giuliani's three concertos will be selected. Since we just eliminated J as an option, this means that the remaining two of Giuliani's concertos - H and K - must be selected. So, we can accurately say that K must be selected if O is selected for the first Sunday.

Does that make sense? Please let us know if you have any other questions and best of luck with your studies!