Maryland Math 2.NOS.C.9

2.NOS.C.9 is a cluster heading. These are the individual standards under it.

• 2.NOS.C.9.a

  Use concrete models or drawings to add and subtract.

• 2.NOS.C.9.b

  Use strategies based on place value (counting on, partial sums, making tens, etc.) to add and subtract.

• 2.NOS.C.9.c

  Use properties of operations, and/or the relationship between addition and subtraction to add and subtract.

• 2.NOS.C.9.d

  Represent and explain the calculation by connecting the strategy used to the meaning of addition and subtraction.

01

What Students Need to Do

Students find sums and differences within 1,000 by working with hundreds, tens, and ones. They use blocks or drawings to show trades between places and explain how the model matches their calculation.

02

What Mastery Looks Like

A student can solve 268 + 175 and show where they make a new ten and a new hundred. They can solve 403 - 176 by trading across the empty tens place, then check their answer with addition.

03

Common Misconceptions

Students may combine digits without matching place values, or subtract the smaller digit from the larger in each column. When solving 403 - 176, they may make ten tens but forget to reduce the hundreds from four to three.

04

How to Assess It

Give this exit ticket: Solve 403 - 176. Draw and label each trade, then use addition to check your answer.

1. 01

   Build 236 and 187 with base-ten blocks, combine matching places, then trade ten ones for a ten and ten tens for a hundred.

2. 02

   Ask, 'How can you subtract 175 from 402 when there are no tens?' Have students sketch and explain each trade.

3. 03

   Put 326 + 158 and 504 - 267 on cards; partners draw place-value models, solve, and swap cards to check answers.

4. 04

   A library has 348 books and gets 176 more; students draw hundreds, tens, and ones to find the new total.

• 2.NOS.A.1

  Use understanding of 100 as a bundle of ten tens, called a “hundred,” and compose and decompose three-digit numbers.

• 1.NOS.E.10

  Add within 100 including adding a two-digit number and a one-digit number and adding a two-digit number and a multiple of 10. Understand that when adding two-di...

• 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-...