The five lockers that are toggled exactly twice are lockers numbered 2, 3, 5, 7 and 11. These are all prime numbers, which have only two factors—1 and the number itself—so they are touched just twice during the process.
Class 8 Mathematics Ganita Prakash Chapter 1 A Square and A Cube NCERT solutions
Class 8 Mathematics Chapter 1 A Square and A Cube question answer
The five lockers that are toggled exactly twice are locker numbers 2, 3, 5, 7 and 11. These are prime numbers and have exactly two distinct factors—1 and themselves. This means they are toggled only by person 1 and one other person (themselves), resulting in exactly two toggles. Khoisnam uses this knowledge to extract the code clue from these specific lockers that were touched only twice during the puzzle.
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