Hard 3 challenges Grade 2 thinkers to find patterns in three-digit number sequences such as 120, 140, 160, and 180. Second graders answer four multiple choice questions about skip-counting rules and missing numbers in a sequence, then complete five fill-in problems that continue or extend a pattern. Clear hints guide second graders to check the difference between side-by-side numbers to find whether the rule is adding 5, 10, or 100 each step.