8. Xiao Ming and Xiao Dong participate in a math exam at the same time. Xiao Ming first reads through the entire paper before starting to solve the problems; it takes him an average of 1 minute to read a question; Xiao Dong spends 10 minutes deciding the order of the questions to solve before starting. Xiao Ming takes an average of 1 minute to solve a question, while Xiao Dong takes an average of 1.6 minutes to solve a question, and they finish at the same time. This test paper has $\qquad$ questions.
$25$