mtbcupg

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Solved! 💜 += 25;

As you leaf through the files, you recognize the problems from the 2010 IMO hosted in Astana, KAZAKHSTAN.

So, the world around you is perhaps ten years behind? That explains why the camp is still called MOSP, you think.

Still, the classrooms around here don’t look familiar at all.

You look around you and realize that you must be in Lincoln, Nebraska, not at Carnegie Mellon. No wonder MOSP was so much nicer and more spacious than MOP has been. Does that mean the Steve you met was actually Steve Dunbar? You wonder to yourself just how parallel this world is.

Evan would be so happy to be here, you think to yourself. He’d be going on and on about the “good old days”. Well, you can kind of see why, now that you’re seeing it all for yourself. You make a mental note to visit Selleck at some point, to see if the dining hall here is really as good as Evan claims it is.

For now, you head back out to look around the Lincoln campus some more.

Click the image to continue.
Lincoln, NE.

Solution to mtbcupg

Like in the earlier Gradescope puzzle, the only initially given data is the title of the puzzle. The puzzle title is a join code for a Google Classroom, and entering it, one finds a class called Solve Identify Sort Index. The banner of the puzzle is depicted below.

Banner

The title refers to four steps:

  1. Solve the math problems.
  2. Identify the six answers that are out of place as past IMO problems.
  3. Sort by problem number.
  4. Index by problem number into answer.

Solve

The first step in the puzzle is to solve the various math problems. Solvers are given a chance to check their answers once for the problems by submitting in the classroom, but this step is not essential, and is only to help check the team’s work.

Here are all the answers:

Code Ans
A1 0
A2 20
A3 19
A4 2
A5 16
A6 15
A7 14
C1 13
C2 18
C3 12
C4 11
C5 10
C6 8
C7 4
N1 9
N2 7
N3 6
N4 5
N5 3
N6 1
N7 17

Identify

There are six problems whose answers are conspicuously out of place; otherwise the answers are in descending order from 20 to 0. Given the shortlist flavoring of the problem statement it makes sense to look up the IMO problems in those slot. Indeed, they were problems that corresponded to IMO problems (and none of the other problems do so).

Code Ans IMO Problem
A1 0 IMO 2000/2
A4 2 IMO 2002/5
C2 18 IMO 2018/4
C7 4 IMO 2004/3
N1 9 IMO 2009/1
N7 17 IMO 2017/6

Sort

The six obtained problem numbers are distinct, so sort the above table by the problem number.

Code IMO Problem
N1 IMO 2009/1
A1 IMO 2000/2
C7 IMO 2007/3
C2 IMO 2018/4
A4 IMO 2002/5
N7 IMO 2017/6

Index

We need to put three-letter codes for each of the six problems. The obvious choice is the proposing country; a full list is given on evanchen.cc for convenience, but AoPS should work well too. The authors are:

Code IMO Problem Author
N1 IMO 2009/1 AUS
A1 IMO 2000/2 USA
C7 IMO 2007/3 EST
C2 IMO 2018/4 ARM
A4 IMO 2002/5 IND
N7 IMO 2017/6 USA

Then index as shown in the diagram.

Code IMO Problem
N1 IMO 2009/1 A U S
A1 IMO 2000/2 U S A
C7 IMO 2007/3 E S T
C2 IMO 2018/4 A R M
A4 IMO 2002/5 I N D
N7 IMO 2017/6 U S A

This gives the phrase ASTANA. This was the location of IMO 2010, and the capital of KAZAKHSTAN.

Author Notes

This puzzle is actually described in Evan’s mystery hunt puzzle blog post: the idea was originally meant for the much more difficult puzzle The IMO Shortlist, where it was promptly scrapped in favor of a different one. I figured to bring the mechanism back to use here, with problems that simply gave answers (rather than the more complicated mechanic given in the Mystery Hunt puzzle).

I didn’t mean to skip the geometry section, it just ended up that way because there was no way to get the word ASTANA while using one of the geometry problems, and that cluephrase was so fitting I couldn’t resist. In general, if you’re curious, here is the set of possible six-letter phrases. (The answer AUTHOR would have been pretty good too, I guess.)

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