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Common Core Math1st GradeNumbers in Base Ten

1.NBT.2: Understand Tens and Ones

Also written as 1.NBT.B.2 and CCSS.MATH.CONTENT.1.NBT.B.2 · Cluster: Understand place value.

Get the Place Value ChartAll 21 1st Grade Math Standards

The Official Wording

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, Grade 1, Number & Operations in Base Ten · Read it at the source · Checked October 14, 2026

What 1.NBT.2 Means in Plain English

First graders see that 47 means 4 tens and 7 ones, and can bundle 47 straws to show it. Three cases get extra attention: 10 is one bundle of ten ones, the teens are a ten plus 1 to 9 ones, and 60 is six tens and 0 ones.

The teens are the trap, because “fourteen” says the four first while 14 writes the one first. Students who bundle and unbundle with ease compare numbers by their tens (1.NBT.3), and in 2nd grade stretch the idea to hundreds (2.NBT.1).

1.NBT.2 I Can Statements

  • I can tell how many tens and ones are in a number.
  • I can show that 10 is a bundle of ten ones.
  • I can build teen numbers as a ten and some ones.

1.NBT.2 Worked Example

One two-digit number in two columns, where the 4 is really four bundles of ten.

47 by place value
4Tens
7Ones
Build it with straws: 4 bundles of ten and 7 loose straws. Count the bundles by tens, 10, 20, 30, 40, then count on the loose ones: 41 to 47.
40 + 7

forty-seven

Common Mistakes with 1.NBT.2

Reversing the teens

Fourteen written as 41

Try this: Build fourteen with one ten-bundle and four loose straws, then write the bundle’s digit first, because tens always go on the left.

Reading the tens digit as ones

In 47, says the 4 means four straws

Try this: Point to the 4 and have the student hand over what it stands for: four bundles, forty straws, not four loose ones.

Not seeing a ten as one thing

Asked how many tens are in 30, counts thirty single cubes

Try this: Snap cubes into trains of ten, then ask for 30 using only trains so students count tens: one, two, three tens.

Where 1.NBT.2 Fits

Comes BeforeK.NBT.1Build the numbers 11 to 19 as ten ones and some further ones.
Alongside1.NBT.1Count, read and write numbers to 120.1.NBT.3Compare two two-digit numbers using their tens and ones.
Comes Next1.NBT.5Find 10 more or 10 less than a two-digit number without counting.2.NBT.1Read three-digit numbers as hundreds, tens and ones.

Practice 1.NBT.2

Math Worksheet GeneratorFree ToolTwo-digit place value at the 1st grade level with an answer key: tens and ones from a numeral, and the numeral from a picture of rods and cubes.Grade 1Place valueAnswer key
Make a Worksheet

Quick Check

  1. How many tens and ones are in 63?
  2. What number is 1 ten and 8 ones?
  3. Mr. Bell has 5 bags of 10 pencils and no loose pencils. How many pencils does he have?

1.NBT.2: Other Names

1.NBT.21.NBT.B.2CCSS.MATH.CONTENT.1.NBT.B.2

Common Core State Standards © Copyright 2010. National Governors Association Center for Best Practices and Council of Chief State School Officers. All rights reserved. Official wording from the Common Core State Standards PDFs at corestandards.org, last checked October 14, 2026. The explanation, I can statements, example, mistakes and practice on this page are EMStudio’s own, written beside the official wording. They are not part of the standard.