MathDB
juniors scanning rectangles for treasure

Source: Canadian Junior Mathematical Olympiad 2024 /1 easier version of CMO P4 https://artofproblemsolving.com/community/c6h3272717p3011

March 24, 2024
combinatorics

Problem Statement

Centuries ago, the pirate Captain Blackboard buried a vast amount of treasure in a single cell of a 2×42 \times 4 grid-structured island. Treasure was buried in a single cell of an M×NM\times N (2M2\le M, NN) grid. You and your crew have reached the island and have brought special treasure detectors to find the cell with the treasure For each detector, you can set it up to scan a specific subgrid [a,b]×[c,d][a,b]\times[c,d] with 1ab21\le a\le b\le 2 and 1cd41\le c\le d\le 4. Running the detector will tell you whether the treasure is in the region or not, though it cannot say where in the region the treasure was detected. You plan on setting up QQ detectors, which may only be run simultaneously after all QQ detectors are ready. What is the minimum QQ required to gaurantee to determine the location of the Blackboard’s legendary treasure?