Q21

[steves]

Not sure how to approach Q21 or 22. I find few inferences from the diagram, leaving most options appearing to be possibly true. Manually plugging in each option and seeing if it can't be true would seem to take a huge amount of time.

[maryadkins]

I don't see much of a way around plug and chug on this one. Turns out though, it doesn't actually take a huge amount of time given that it's such a constrained game with only 5 empty slots and a lot of cascading rules once you are given a new "known" by an answer choice. It's also a good opportunity to use previous work.

On 21, if you plug in (A)—that no January ticket is green—you know that line 3 in Feb. must be green, and that lines 1 and 3 in Jan. have to be red or yellow. You also know that the other two lines in Feb. (lines 1 and 2) must be red or yellow. Pick red or yellow for each to see if it works out, and it does!

Moving on.

In Question 22, just envision (A)—greens in those slots—and it doesn't leave any room for a green for either month in line 3. So it's out. In (B), you've already done the work in Question 21 to show that it's possible.

You're right that this kind of work isn't ideal, but it's also sometimes necessary, so might as well get good at it. When you don't see another way, just plug and chug as quickly and methodically as you can, and wherever possible, use previous work!