Hello everybody

For a research project (study) I'm searching math tasks ordered by difficulty (easy to hard) and average time needed to solve. I think and I hope that there is also some ordering according to difficulty level in the SAT tests. I would prefer if the difficulty level is inferred from the analysis of the performance of participants instead of the estimation of a single person (but latter would also be acceptable).

Does somebody know a resource which provides such an ordering of difficulty level and perhaps also the average time to solve for the tasks?