Understand that the two digits of a two-digit number represent amounts of tens and ones. Understand the following as special cases:

  • a. 10 can be thought of as a bundle of ten ones — called a “ten.”

  • b. The numbers from 11 to 19 are composed of a ten and one, two, three, four, five, six, seven, eight, or nine ones

  • 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).

Lesson Planning and Activity Resources

1.NBT.2 Marilyn Burns diagnostic interview with a student.

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1.NBT--Interactive games for Numbers & Operations in Base Ten

Grade 1 Unit: Understanding Place Value
(from Georgia Department of Education)
This unit addresses KCAS 1.NBT.2-6 and 1.MD.4.
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First Grade Unit: Exploring Two-Digit Numbers

(from North Carolina Dept. of Public Instruction)

This unit addresses 1.NBT.1, 2, 3, 5 and 1.OA.6.
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1.NBT.2 Lesson: Tall Towers
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1.NBT.2 Lesson: Handful of Cubes
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Interactive Material -
Use the buttons to create multiples of 10.
The worksheets have:
  • equations that are breaking apart a two digit number into tens and ones.
  • writing a number based on the tens and ones.
  • identifying the value the place value blocks represents.