CCSS.Math.Content.2.NBT.B

CCSS.Math.Content.2.NBT.B is a cluster heading. These are the individual standards under it.

• CCSS.Math.Content.2.NBT.B.5

  Fluently add and subtract within 100 using strategies based on place value, properties of operations, and/or the relationship between addition and subtraction.

• CCSS.Math.Content.2.NBT.B.6

  Add up to four two-digit numbers using strategies based on place value and properties of operations.

• CCSS.Math.Content.2.NBT.B.7

  Add and subtract within 1000, using concrete models or drawings and strategies based on place value, properties of operations, and/or the relationship between a...

• CCSS.Math.Content.2.NBT.B.8

  Mentally add 10 or 100 to a given number 100—900, and mentally subtract 10 or 100 from a given number 100—900.

• CCSS.Math.Content.2.NBT.B.9

  Explain why addition and subtraction strategies work, using place value and the properties of operations.

01

What Students Need to Do

Students solve sums and differences within 1000 by breaking numbers into hundreds, tens, and ones. They use drawings, equations, and mental strategies, and explain each regrouping. They also find 10 or 100 more or less without counting by ones.

02

What Mastery Looks Like

A student chooses an efficient strategy and gets accurate answers, including sums of several two-digit numbers. They align place values, regroup correctly, and use addition to check subtraction. They can explain why the method works.

03

Common Misconceptions

Students may line up digits by the left edge or treat zeros as if they hold no place. They may calculate each column without making a new ten or opening a hundred. In subtraction, some always take the smaller digit from the larger one.

04

How to Assess It

Exit ticket: Solve 368 + 247 and 602 − 178, then explain one regrouping with a quick base-ten sketch.

1. 01

   Have pairs model 346 + 278 with base-ten blocks, trade units as needed, and record each trade beside a written equation.

2. 02

   Ask students to draw and explain why 402 minus 186 requires decomposing a hundred, then compare explanations with a partner.

3. 03

   Play Target 500: students draw digit cards, make two numbers, then add or subtract to get as close to 500 as possible.

4. 04

   Give students a $1,000 classroom budget with whole-dollar prices, then have them choose supplies and calculate the total and money left.

• CCSS.Math.Content.1.NBT.C

  The 1st Grade version of this standard.

• CCSS.Math.Content.1.OA.B

  Understand and apply properties of operations and the relationship between addition and subtraction.

• CCSS.Math.Content.4.NBT.B

  Use place value understanding and properties of operations to perform multi-digit arithmetic.

• CCSS.Math.Content.3.NBT.A

  Use place value understanding and properties of operations to perform multi-digit arithmetic.