CCSS.Math.Content.1.NBT.B.2
The standard
Understand that the two digits of a two-digit number represent amounts of tens and ones. Understand the following as special cases:
Common Core State Standards for Mathematics
What this standard means
Students need to see a two-digit number as groups of ten and leftover ones. They should build numbers with ten-sticks and single cubes, say how many tens and ones, and connect that to the written digits.
Mastery looks like explaining that 47 is 4 tens and 7 ones, not just “4 and 7.” Students often get stuck with teen numbers, especially 11 to 19, and with numbers like 30, where there are no extra ones.
Ways to teach it
- Have students build numbers from 10 to 99 with base-ten rods and unit cubes, then label each build with a tens and ones card.
- Ask students to write about 16 using the sentence frame, “16 has ___ ten and ___ ones, so I built it with ___.”
- Show 52, 18, 40, and 73, and have students draw quick tens and ones sketches on mini whiteboards.
- Use a classroom supply count, such as 34 pencils, and bundle them into groups of ten with leftovers to record tens and ones.
Plan a lesson for CCSS.Math.Content.1.NBT.B.2
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Related standards
- CCSS.Math.Content.1.NBT.B.3
Compare two two-digit numbers based on meanings of the tens and ones digits, recording the results of comparisons with the symbols >, =, and <.
- CCSS.Math.Content.4.NBT.A.1
Recognize that in a multi-digit whole number, a digit in one place represents ten times what it represents in the place to its right.
- CCSS.Math.Content.2.NBT.A.1
Understand that the three digits of a three-digit number represent amounts of hundreds, tens, and ones; e.g., 706 equals 7 hundreds, 0 tens, and 6 ones. Underst...
- CCSS.Math.Content.5.NBT.A.1
Recognize that in a multi-digit number, a digit in one place represents 10 times as much as it represents in the place to its right and 1/10 of what it represen...