Part 2: Coursebook ch. 4-32, Game 1, February 92

[Lina]

Hi, I am reviewing game 1, February 92, and need help understanding question #17

I have trouble seeing what would change if Tuesday was moved to an earlier part of the day. How does this change affect the other variables?

Thanks for your help

[Jon Denning]

Hey Lina - thanks for the question. I'm guessing you looked through the explanation on 4-108, so I'll try to add to that.

17. First off, the question tells us that 4 is moved from the morning to the afternoon on Tuesday, so I wonder if perhaps a misunderstanding of that is what caused issues (that is, Tuesday is not moved at all, and 4 is moved to a later time on Tuesday, not an earlier time).

The biggest changes you see when you move 4 from Tues morning to Tues afternoon is that the two remaining afternoon spaces (Thurs, Fri) must be filled by 2 and 5 (don't know the order), which means the only open space after 4 is Wed morning so that is taken by 6, and then 1 and 3 must fill the mornings of Mon and Tues (don't know the order). That's a fairly complete diagram, which we can then use to quickly find the answer that is not necessarily true (note: the four wrong answers all must be true, so those should be easy to spot as well).

A. True. 1 is Mon or Tues, 2 is Thurs or Fri afternoon.
B. Not Necessarily True. 2 and 5 are Thurs and Fri, but we don't know the order (see above).
C. True. Just like A, 3 is Mon or Tues, 2 is Thurs or Fri afternoon.
D. True. 6 is Wednesday morning, 5 is Thurs or Fri afternoon.
E. True. 7 is Thursday morning, 2 is Thurs or Fri afternoon.

I hope that helps!