//------------------------------//
// Puzzle 6 solution 
// Story: School of Logic: a Collection of Puzzles involving the Student Six 
// by Coyotek4 
//------------------------------//

Rarity gives Gallus an odd look. “I beg your pardon?”

Gallus pauses for a few seconds before responding. “Professor, how long did it take for you to figure out an appropriate ‘ensemble’ for your client?”

“Oh … I don’t remember, really … maybe, a couple hours?”

“I see,” Gallus replies. He turns to his fellow students. “Ocellus, did you write down the requests made by Rarity’s client?”
Ocellus looks up from her sheet of notebook paper, gives a sheepish smile, and nods.

“Professor, may I come to the board?”

“Well … uh … yes, that would be OK.”

Gallus takes the paper from Ocellus’s desk and casually writes down a number of sentences on the board:



No dress should have more than one gem type, and at least three different gem types had to be used for the dresses, though not necessarily all four gem types.
C must wear sapphire, unless D wears ruby.
D must wear emerald, unless B wears the same gem type as E.
E must wear either sapphire or emerald, with A wearing diamond if E wears sapphire and with A wearing ruby if E wears emerald.
C should wear ruby, unless B wears either sapphire or emerald, and if B does wear sapphire then C should wear diamond, and if B wears emerald instead then C should wear emerald as well.



“That’s all the information, correct?” Gallus dryly asks his fellow students. They nod in unison. “Ocellus, care to begin?”

Ocellus responds quickly: “The last request indicates that C should wear either ruby, diamond, or emerald. That means that C should not wear sapphire. But then there’s the request that C must wear sapphire unless D wears ruby … since C cannot wear sapphire, that means that D must wear ruby.”

“Wow … I’m very impressed with your acumen, Ocellus. And yes, D did indeed wear ruby. But then—”

“Sandbar,” Gallus continues, “what do you see?”

Sandbar studies the requests for another minute. “Ocellus said that D wore ruby. But that one requests says that D should wear emerald, unless B and E wear the same gem type. And that means that B and E have to wear the same gem type.”

Gallus turns to Yona. “Your turn.”

“What? Oh, yeah, Yona ready. Uh … B and E wear same gem, but E wear either sapphire or emerald, so that mean B also wear either sapphire or emerald. And if B wear sapphire, then C wear diamond, and if B wear emerald, then C wear emerald.”

“Smolder?”

The young dragon sighs. “If B and E both wear emerald, then C wears emerald as well. And if E wears emerald, then A wears ruby. But D already wears ruby, so everyone would be wearing either emerald or ruby, and that can’t be since at least three gem types have to be used.”

“Silverstream? Care to finish?”

The hippogriff enthusiastically continues: “That means B and E must both wear sapphire instead, and since B wears sapphire that means C wears diamond, and since E wears sapphire that means A wears diamond.”

“So in summary,” Gallus concludes as he strolls back to his seat, “A wears diamond, B wears sapphire, C wears diamond, D wears ruby, and E wears sapphire.”

Rarity gapes in astonishment before sputtering with a response. “What? … but … I mean … that’s all correct, but … I spent hours on … and you just …”

“We’ve had a lot of practice as of late,” Gallus casually admits. “Now I can’t believe what I’m about to say, but can we get back to discussing fashion?”