Question 13.5.2

Imagine a grid of six north-south lines, and six east-west lines. You want to walk along the lines of the grid from the south-west corner ($A$) to the north-east corner ($B$) in the shortest way possible, so without any walking back west or south. One possible path through the grid is shown below. Diagram: gridwalk 2 How many different paths are there?

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