Six. In mathematics, Cong Conghua bought a model plane in 65 yuan. 65 divided by 10, the result is 6.5, that is, Cong Cong paid at most 6 pieces 10 yuan. Mathematics is a universal means for human beings to strictly describe the abstract structure and mode of things, and can be applied to any problem in the real world. All mathematical objects are artificially defined in essence.