Illustrative MathematicsVaries

This task was designed to support students in developing the concept of ten more and ten less, moving from concrete representation to understanding of the unit of ten within ten more and ten less. Students will also understand the value of ten(s) within any number as they mentally add or subtract 10 from a given number 100-900. Teachers may want to repeat the lesson a second time starting with a different number, such as 8. Then they could compare the two charts and look for similarities and differences.