A coach arranged 6 players, each with different height in two parallel
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13 Sep 2021, 10:24
Very cool question!
For this one, I would start by numbering the players 1-6 respectively.
1 2 3
4 5 6
How many times can we permute this matrix within the constraints?
Before we start, it's important to note that player 1 and player 6 can never move positions, otherwise, the left-to-right constraint will be violated.
So we begin by assessing how we can create the top row.
We have:
1 2 3
or
1 2 4
or
1 2 5
or
1 3 4
or
1 3 5
You'll see that the bottom row fills itself in each example.
The question now becomes, can we create any more top rows?
For example, can we create 1 4 5?
The answer is no, because the only numbers greater than 4 are 5 and 6, and 5 is already in the top row and remember, 6 cannot move from that bottom row spot.
Therefore, the maximum number of arrangements is 5, so the answer is B