Maryland Math K.NOS.C.9.a

MathKindergartenNumber and Operation Sense

The Standard

K.NOS.C.9: Understand 10 as a group, collection, or bundle of ten ones called a “ten.”

Compose and decompose numbers from 11 to 19 into ten ones and some further ones by using objects or drawings, and equations (e.g., 13 = 10 + 3).

Maryland College and Career Ready Standards for Mathematics (2025) · DEVELOP FOUNDATIONS FOR PLACE VALUE.

Teacher's field guide

What Students Need to Do: Students build a number from 11 to 19 with ten counters and some extra counters. They separate the ten from the extras, then put them back together. They show both parts in a drawing and an equation.
What Mastery Looks Like: Given 17 counters, a student groups ten and leaves seven loose. They draw the two groups, write 17 = 10 + 7, and explain that the group of ten is worth ten.
Common Misconceptions: A student may count a group of ten as one object and write 17 = 1 + 7. Another may draw seven extra dots but write 17 = 10 + 6.
How to Assess It: Exit ticket: Draw 16 dots, circle ten, and complete 16 = 10 + __. Ask students to point to the dots that fill the blank.

Lesson moves

Give each child 18 linking cubes to snap ten into a stick, leave eight loose, and record 18 = 10 + 8.
Show a full ten-frame and five extra counters; ask, “Why is this 15 and not 6?”
Give pairs teen-number cards and ten-frame drawings with extra dots; have them match each pair and say the equation.
Put ten classroom pencils in a cup and four beside it; ask students to count them and write 14 = 10 + 4.

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