CCSS 1.NBT.2C (Common Core, 1st Grade): "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)." The worksheets below practice this standard. Each one is a free printable PDF with an answer key, comes in multiple versions, and can also be assigned digitally - no login or account needed.
Number and Operations in Base Ten Understand place value.2Understand that the two digits of a two-digit number represent amounts of tens and ones. Understand the following as special cases:cThe 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).