Understand place value.
Understand that the two digits of a two-digit number represent amounts of tens and ones; Understand special cases A, B, C.
c. The numbers 10, 20, 30, 40, 50, 60, 70, 80, 90 refer to one, two, three, four, five, six, seven, eight, or nine tens (and 0 ones).
More information and the complete College and Career Readiness Standards can be found here.