Description: Topic C builds on students' Grade 2 work with comparing numbers according to the value of digits in the hundreds, tens, and ones places. Lesson 12 formally introduces rounding two-digit numbers to the nearest ten. Rounding to the leftmost unit usually presents the least challenging type of estimate for students, and so here the sequence begins. The number line, presented vertically, provides a new perspective on a familiar tool. Students continue to use the vertical number line in Lessons 13 and 14. In Lesson 13, the inclusion of rounding three-digit numbers to the nearest ten adds new complexity to the previous day's learning. Lesson 14 concludes the module as students round three- and four-digit numbers to the nearest hundred.*Teacher Advisor is 100% free.