Math Grade 1 Quiz 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)-1.NBT.B.2.C

This standard focuses on understanding the numbers 10 through 90 in increments of ten. Each of these numbers represents a certain number of tens and zero ones. For example, the number 30 signifies three tens and zero ones. This foundational understanding of place value ensures that students recognize the value of each digit in a two-digit number. Understanding this also prepares students for further study of place value in larger numbers and operations involving tens and ones.