MathDB
Lattice points - Number of paths

Source: South Africa 1999

September 30, 2005
combinatorics unsolvedcombinatorics

Problem Statement

You are at a point (a,b)(a,b) and you need to reach another point (c,d)(c,d). Both points are below the line x=yx = y and have integer coordinates. You can move in steps of length 1, either upwards of to the right, but you may not move to a point on the line x=yx = y. How many different paths are there?
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