Maryland Math 2.NOS.A.1.c
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 in more than one way (e.g., 439 = 400 + 39 or 439 = 435 + 4).
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 split a three-digit number into parts in more than one way. They put the parts back together and show that the total stays the same.
What Mastery Looks Like
- Given 426, a student can write 400 + 26, 420 + 6, and 410 + 16. They can use blocks, a drawing, or addition to show why each sum equals 426.
Common Misconceptions
- Some students think 400 + 20 + 6 is the only way to split 426. Others trade a ten for ten ones but forget to reduce the number of tens.
How to Assess It
- Exit ticket: Write 426 as two different sums of two numbers. Check both sums with a drawing or addition.
Lesson moves
Ways to Teach It
Build 246 with base-ten blocks, trade one ten rod for ten ones, and record both splits as addition sentences.
Ask, 'Are 300 + 74 and 360 + 14 both 374?' Have students explain their answer with a sketch.
Give pairs of students cards showing 438, 400 + 38, 420 + 18, and 430 + 8 to match and check.
Show a 365-cent receipt and use play money to group the amount as 300 + 65 cents, then 360 + 5 cents.
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Printable 2.NOS.A.1.c Worksheet
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Related Standards
- 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).
- 2.NOS.A.1.a
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-...
- 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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