A few of my students love intellectual challenges and I usually start them off with these.
Included are sets of 160, 120, 80 or 40 problems. Each set has an answer key as well.
Like every other offering here, these are representative are a LOT MORE problems and are in grade-domain-cluster-standard-difficulty level order.
[The problems in All WORKSHEETS and PREVIEWS are printed in difficulty (1 [easy], 2 [not so easy], 3 [proficiency] up to 4 [mastery]) order within a skill. The actual difficulty level appears slightly to the left of the DK box of each problem in a very small font. Also, instructional references appear on worksheets but are optional on quizzes.]