This easy worksheet zeroes in on the hardest decade jumps in the 0-120 sequence. Students trace the counting words 'hundred,' 'twenty,' 'digit,' 'number,' and 'tens' in Part A, then tackle four fill-in-blank prompts in Part B: what comes after 99, what comes before 120, the next number in 67, 68, 69, ___, and what comes after 109. Part C wraps with three true-or-false items checking that 120 follows 119 and that 101 comes after 100. Targeted practice for the 99-to-100 and 109-to-110 transitions where first graders most often stumble.