Compose and decompose numbers from 11 to 19 into ten ones and some further ones, e.g., by using objects or drawings, and record each composition or decomposition by a drawing or equation (such as 18 = 10 + 8); understand that these numbers are composed of ten ones and one, two, three, four, five, six, seven, eight, or nine ones.




The concept of tens and ones is the foundational basis for our number system. Further, students’ early grasp of the number system is critical in all other areas of mathematics. Students should be composing and decomposing a teen number and representing it, using objects, drawings, or an equation, as a bundle of ten ones and an appropriate number of remaining ones.

Understanding the Standard:

  • Students should be exposed to the idea of bundling 10 ones to make a unit of ten. Often, this is referred to as “making a trade”.
  • Students need opportunities to work with decomposing two-digit numbers in order to see the value of each digit. The use of manipulatives and technologies, which allow students to physically make bundles of tens, helps with moving an abstract concept into more concrete terms.
  • As in the case of the number 14, students should be able to move fluently (quickly and easily) between the concept of 14 ones being the same as 1 ten and 4 ones.

Questions to Focus Instruction:

  • What specific opportunities and activities will enhance students’ understanding that 10 ones is the same as 1 ten?
  • Do students understand that two-digit numbers from 11 through 19 are composed of 1 ten and a specific number of ones?
  • Can students bundle a group of 10 ones into a ten and understand that both have the same value?


Prior to: Students can count, write, and recognize numbers from 1 to 19. Additionally, they can create sets that are representative of that number.

At grade level:
Students compose and decompose numbers 11 through 19, recognizing that two-digit numbers are composed of a bundle of 10 and some ones.

Beyond Grade Level:
After learning to compose and decompose a two-digit number into bundles of tens and remaining ones, student will use that knowledge to compare two-digit numbers with one another. Go to 1.NBT.B.2b to see the progression of related skills.