On Erdos' ten-point problem

Around 1994, Erdoset al. abstracted from their work the following problem: “Given ten pointsAij, 1≤i≤j≤5, on a plane and no three of them being collinear, if there are five pointsAk, 1≤k≤5, on the plane, including points at infinity, with at least two points distinct, such thatAi, Aj, Aij are collinear, where 1≤i≤j≤5, is it true that there are only finitely many suchAk's?” Erdoset al. obtained the result that generally there are at most 49 groups of suchAk's. In this paper, using Clifford algebra and Wu's method, we obtain the results that generally there are at most 6 such groups ofAk's.