Calculating Rabbit's Moves on a Chessboard | Combinatorial Question

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Discussion Overview

The discussion revolves around calculating the number of distinct paths a rabbit can take on a chessboard from the cell (1,1) to the cell (3,4), given that the rabbit can only move right or upwards. The conversation explores combinatorial methods and reasoning related to this problem.

Discussion Character

  • Exploratory
  • Mathematical reasoning
  • Debate/contested

Main Points Raised

  • One participant suggests that the total moves on the chessboard could be calculated using combinations, specifically (64 C 8), but struggles with the specific path from (1,1) to (3,4).
  • Another participant recommends drawing the chessboard and tracing possible paths to identify patterns.
  • A different participant notes that the rabbit's movement restrictions (only right or upwards) limit the number of paths significantly.
  • One participant mentions a combinatorial shortcut for calculating paths and suggests that understanding the problem is crucial.
  • Another participant expresses intent to estimate the number of paths and share their result for validation.
  • A participant claims to have found 10 distinct ways for the rabbit to move right and up on the chessboard.
  • One participant inquires about the method used to arrive at the 10 ways.
  • A later reply provides a formula for calculating paths to (m,n) using factorials, illustrating the combinatorial approach with specific examples.
  • Another participant emphasizes the importance of the problem-solving process over the final answer, encouraging exploration and experimentation.

Areas of Agreement / Disagreement

Participants express various methods and reasoning for solving the problem, but no consensus is reached on a definitive approach or answer. Multiple viewpoints and methods are presented without resolution.

Contextual Notes

Some participants reference broader combinatorial principles and methods, but the discussion does not resolve the specific calculations or assumptions involved in the pathfinding problem.

ParisSpart
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A rabbit lives on an ordinary chessboard 8x8. The rabbit located over the cell (1.1) (lower left, the upper right corner is (8.8), the lower right corner is (8,1)). At any time the rabbit jumps either to the right or upwards.

How many different ways can move the rabbit to reach the cell (3.4)?


I have a problem here.I think all the moves in the chessboard is (64 C 8) like (n C k) combinations, but i can not think how to move from the cell (1.1) to (3.4) maybe someone can give me any suggestion how?
 
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To understand the problem - draw out the chessboard and locate the cells.
Start tracing out possible paths manually - at some point you'll see a pattern emerge.
 
but the there are a lot of paths... maybe we can find another way to find them with combinatorial types?
 
Rabbit can only move right or upwards though - that severely restricts the number of paths.

Of course there is a shortcut involving combinations etc.
Your problem is how to find it - with the first step being to understand the problem.

Another way: since you already solved how to get to (8,8) from (1,1) ... presumably you can do it for any size square board?
So how does that work?
 
i will try to estimate it and i will post the result here to find out if its correct
 
i find it there are 10 ways to move right and up in the chessboard!
 
well done - how did you do that?
 
The rabbit reaches (8,8) from (1,1) in 14C7= 14!/(7!.7!) ways, if the rabbit jumps only one square at a time.
Call a rightward jump 'R' and upward jump 'U'. The answer is the total number of linear permutation of 7 R's and 7 U's.
Similarly, to reach (m,n) the rabbit can move in
(m+n-2)!/ [(m-1)!(n-1)!] ways.
 
Last edited:
Well done.
The answer is not so important as how you got to it.
Also I hope you can see that you sometimes have to mess about with a problem for a bit before finding out the short, simple, way to do it. Don't be scared to start a problem without knowing how to get to the answer.
 

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