Q21

[IsaacS982]

Can someone post an efficient explanation? I had to try a bunch of different solutions and it took longer than it should have.

[ohthatpatrick]

First we would write the new rule
K - M
on our page (near Q21), and then try to connect other rules to that if possible.

By adding rule 2 and 3, we have GK - M - J

By adding rule 4, we have L - F - GK - M - J

That's 6 of the 7 people accounted for. We just have to worry now that there are at least two between H and M.

That means it's impossible for H to go LATER than M (since only J could come in between).

So H must go earlier than M,
which means H is either before L, before F, or before GK.

If we wanted to write these out, it would look like
H L F G K M J
or
L H F G K M J
or
L F H G K M J

However, we also have the rule that L can't be 2, so we can't do that first one.
Hence, we either have
L H F G K M J
or
L F H G K M J

The 3rd spot could be F or H, so we look and see that (B) is our answer.

Hope this helps.