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Problem of the Week
Problem C and Solution
Corn Maze

Problem

Baljit and Harinder go to a local farm to do a corn maze. The map of the corn maze is given.

A description of the map follows.

On the day they arrive, the farm has the restrictions that they can only travel south, east, or southeast along a path. Using these restrictions, how many different routes can they take from Start to Finish?

Solution

We can solve this problem by tracing out different routes and counting how many we find. We will set up a systematic approach to do so, to ensure that we do not miss any routes.

We begin by labelling the Start with the letter \(S\) and the Finish with the letter \(F\). We label the other seven intersections in the maze as \(A\), \(B\), \(C\), \(D\), \(E\), \(G\), and \(H\), as shown.

The three intersections on the top horizontal
path are labelled S (left end), A (middle), and B (right end). The
intersections on the middle horizontal path are C, D, and E, and the
intersections on the bottom horizontal path are G, H, and F.

Starting at \(S\), Baljit and Harinder can only travel next to \(A\) or \(C\).

Case 1: Baljit and Harinder travel from \(S\) to \(A\).

Since Baljit and Harinder can only travel east, south, or southeast along a path, they have only two choices for where to go next: \(B\) or \(D\).

In total, there are four routes from \(S\) to \(F\) in which Baljit and Harinder first travel from \(S\) to \(A\).

Case 2: Baljit and Harinder travel from \(S\) to \(C\).

Since Baljit and Harinder can travel east, south, or southeast along a path, they have three choices for where to go next: \(D\), \(H\), or \(G\).

In total, there are five routes from \(S\) to \(F\) in which Baljit and Harinder first travel from \(S\) to \(C\).

Therefore, there are a total of \(4+5 = 9\) different routes that Baljit and Harinder can take from Start to Finish.