May 2016 Puzzle

Consider the grid shown in the figure below.  How many different ways are there to get from point A (the bottom left corner) to point B (the top right corner) if you must move along the gridlines in combinations of only upward and rightward moves?

You must show sufficient work to support your answer.

square with 2 deep grid on inside perimeter, point A at bottom left corner, point B at top right cornerView Solution