Quote:
Ariel, Bailey, Corinne, Darryl, Edgar, and Fei are positioning themselves on a flight of six steps for a picture. Darryl and Edgar will be on consecutive steps, but not necessarily in that order. Bailey will be two steps below Ariel, and Fei will be on the step third from the bottom.
If all of the people will be on different steps, select for Bailey the possible steps that Bailey could be standing on for the picture, and select for Corinne the possible steps that Corinne could be standing on for the picture. Make only two selections, one for each column
On these, I like to rule out options from the most restrictive to the least restrictive. We have A, B, C, D, E, and F. F will be third from the bottom. D and E are together, and their order doesn’t matter because we don’t care where they stand, so that brings us down to A, B, C, DE, and F. B will be two steps below A, so B can only be on steps 3 or 5 from the top, and A can only be on steps 1 or 3 from the top. Sometimes drawing a graph and filling it in is easiest.
| Top Step | 2 | 3 | 4 | 5 | 6 |
| Ariel | Corinne | Bailey | Fei | D/E | D/E |
| D/E | D/E | Ariel | Fei | Bailey | Corinne |
Alternatively, you could say D&E can be in spots (1,2), (2,3), (3,4), (4,5), or (5,6).
A and B could be in spots (1,3), (2,4), (3,5), or (4,6)
F has to be in 4, so cross out the options with 4 in them and you get:
D&E can occupy (1,2), (2,3), or (5,6)
A and B can respectively stand in (1,3) or (3,5).
Cross check for double booked spots, and you’ll see that if A and B are in (1,3), then D&E are left with (5,6) and C in 2. If A and B are in (3,5), that leaves D&E in (1,2) and C in spot 6.