Glue-Block Permutation
GMAT glossary · Playbook
Definition
A permutation move that ties items that must sit together into one macro-block, then multiplies block arrangements by internal shuffles.
Glue-Block Permutation in plain English
Use Glue-Block Permutation when items must sit next to each other. Clues include adjacent, together, side-by-side, or must sit next to. Tie the adjacent items into one macro-block. Ways = (n - k + 1 blocks)! times the internal arrangements of the block. Treating glued people as separate multiplies illegal separations; the block enforces adjacency automatically. After the block is formed, you are just permuting fewer units, then restoring the internal shuffle. Micro-example: 5 people in a row, Ana and Ben must sit together. Treat (AB) as one block so you permute 4 units in 4! ways, then multiply by 2 for AB vs BA inside the block: 4! × 2 = 48.
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