Q16

[jennifer]

Why goes the element S have to been included in the photo? I was able to determine that U,Z, W, Y, were in and TR were out? Thank you.

[ohthatpatrick]

Let me quickly diagram the four rules, so we're on the same page:

(1) S --> W
~ W --> ~S

(2) U --> S
~S --> ~U

(3) ~Y --> R
~R --> Y

(4) W --> ~T and ~R
T or R --> ~W

So question #16 tells us that U and Z are in.

U brings in S (rule 2). S brings in W (rule 1). W throws out T and R (rule 4). R being out forces Y in (rule 3).

Chances are you symbolized your original rules backwards. Most students who see this game for the first time incorrectly interpret the first rule as saying "W --> S"

One way to protect against this misinterpretation is to know that words such as
if / all / any / each / any / when / the only
always come before sufficient ideas (left side ideas)
whereas
then / only / only if / must / requires / unless
always come before necessary (right side ideas)

If I said
"Being an American citizen is a quality that every US president has",

we wouldn't want to translate that as
Amer. Cit --> US President

Instead, we want
US President --> Amer. Cit

Mechanically, we can get there by seeing that "every" comes before "US President", so "US president will go on the left side".

The other way to figure out the logic of this 1st rule (and the others, which are phrased in a similar way) is to play around with W and S, in vs. out, to sort out the logic.

If W is in a photograph, do I have to put S in it?

No. Wendy can be in a photograph alone. This rule wouldn't oppose that.

If S is in a photograph, do I have to put W in it?

Yes. Because Wendy is in ALL of Selma's photos. Selma CAN'T be in a photo alone. This rule would preclude that.

Hope this helps.

[jennifer]

Thank you. I see what I did. I made a huge mistake and notated that U->W instead of U->S. It is a shocking that I only answered 2 questions on this game wrong considering what a huge mistake I made.