Interpret two-digit numbers as tens and ones, including cases with more than 9 ones.

This lesson lays a foundation for adding like units within pairs of two-digit numbers. Students interpret numbers as different groups of tens and ones. For instance, they recognize 25 as 1 ten and 15 ones, as 2 tens and 5 ones, and as 25 ones. Working with this concept supports student understanding in the next lessons, when they will add pairs such as 14 + 16 and initially make 2 tens and 10 ones.