Grades 7-8 Video Solutions 2026-2026_7-8

Video Transcription

Video Summary

The transcript solves a counting problem by casework on the first number \(A\) in a permutation of 1–5, with the last number odd and each consecutive triple satisfying a divisibility condition. Most cases fail after checking possible pairs for \(B\) and \(C\). The only valid arrangements found are:

- 2, 1, 3, 4, 5  
- 2, 3, 5, 4, 1  
- 2, 5, 1, 4, 3  
- 4, 3, 1, 2, 5  
- 4, 5, 3, 2, 1  

So, there are <strong>5</strong> valid arrangements.

Keywords

counting problem

permutation

casework

divisibility condition

valid arrangements