The Figure at the Right Shows a 4-Block by 5-Block

Short Answer

The figure at the right shows a 4-block by 5-block grid of streets. Find the number of ways in which you can go from point A to point B , where at each stage you can only go right or up. (You are not allowed to go left or down.) For example, one allowable route from A to B is: Right, Right, Up, Right, Up, Up, Right, Right, Up.