Maryland Math 2.NOS.A.1.a
The Standard
- 2.NOS.A.1
- Use understanding of 100 as a bundle of ten tens, called a “hundred,” and compose and decompose three-digit numbers.
Compose and decompose three-digit numbers into hundreds, tens, and ones by using objects, drawings, and/or equations (e.g., 328 = 300 + 20 + 8 or 328 is thirty-two tens and 8 ones).
Maryland College and Career Ready Standards for Mathematics (2025) · UNDERSTAND PLACE VALUE AND REPRESENTATIONS OF NUMBERS.
Teacher's field guide
What This Standard Means
What Students Need to Do
- Students build and draw three-digit numbers using hundreds, tens, and ones. They write equations to show the value of each part. They also regroup a hundred as ten tens to show the same number another way.
What Mastery Looks Like
- A student can show 328 with 3 hundreds, 2 tens, and 8 ones, then write 328 = 300 + 20 + 8. They can trade the 3 hundreds for 30 tens and explain why 32 tens and 8 ones still make 328.
Common Misconceptions
- Students may write 328 = 3 + 2 + 8, using digits instead of their values. They may think trading a hundred for ten tens changes the number. Some read 32 tens as 32 rather than 320.
How to Assess It
- Exit ticket: Draw 328 with hundreds, tens, and ones. Write one equation using all three units and another using only tens and ones.
Lesson moves
Ways to Teach It
Give pairs base-ten blocks to build 246, then have them trade one hundred flat for ten rods and record both forms.
Ask, 'Can 307 be shown as 30 tens and 7 ones?' Have students sketch their answer and explain it to a partner.
Place digit cards in hundreds, tens, and ones slots; partners write an expanded equation and check it with a quick sketch.
Show a school supply order for 154 pencils; students draw cartons of 100, packs of 10, and singles, then write an equation.
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Printable 2.NOS.A.1.a Worksheet
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Related Standards
- 2.NOS.A.1.c
Compose and decompose three-digit numbers in more than one way (e.g., 439 = 400 + 39 or 439 = 435 + 4).
- K.NOS.C.9.a
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).
- 1.NOS.B.3.a
Compose and decompose two-digit numbers into tens and ones using objects or drawings, and equations (e.g., 10 + 4 = 14; 38 = 30 + 8).
- 1.NOS.B.3.c
Compose and decompose two-digit numbers in more than one way (e.g. 46 = 41 + 5 or 46 = 23 + 23).
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