By Kathy Richardson Assessment #9 Two-Digit Addition & Subtraction Overview & Description of Strategies

Learning to Add & Subtract Two-Digit Numbers Students must understand the underlying math to solve two-digit addition & subtraction problems – otherwise they will simply be following a procedure. They must have a solid understanding of number relationships, number combinations to ten and numbers as tens and ones for two-digit addition & subtraction to have meaning for them. Children must have repeated practice combining, separating, and regrouping numbers.

What are we trying to determine with this assessment? To determine if the student can use the concept of tens and ones to add two-digit numbers, by mentally breaking them apart and reorganizing them into a total number of tens and ones, when the problem is presented 1) using models 2) with the model covered and 3) symbolically

Common Core Alignment Grade 1 Number & Operations in Base Ten Use place value understanding and properties of operations to add and subtract. 1.NBT.4. 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, using concrete models or drawings and strategies based on place value, properties of operations, and/or the relationship between addition and subtraction; relate the strategy to a written method and explain the reasoning used. Understand that in adding two-digit numbers, one adds tens and tens, ones and ones; and sometimes it is necessary to compose a ten. 1.NBT.5. Given a two-digit number, mentally find 10 more or 10 less than the number, without having to count; explain the reasoning used. 1.NBT.6. Subtract multiples of 10 in the range from multiples of 10 in the range (positive or zero differences), using concrete models or drawings and strategies based on place value, properties of operations, and/or the relationship between addition and subtraction; relate the strategy to a written method and explain the reasoning used.

Common Core Alignment continued Grade 2 Number & Operations in Base Ten Use place value understanding and properties of operations to add and subtract. 2.NBT.5. Fluently add and subtract within 100 using strategies based on place value, properties of operations, and/or the relationship between addition and subtraction.

What will my students be asked to do during the Two-Digit Addition & Subtraction assessment? Students will be asked to solve a series of two-digit addition and subtraction problems. They will be asked to solve the problems by grouping/regrouping the numbers into tens and leftovers. They will be asked to use models appropriately to show their thinking, and they will be asked to solve the problems without models.

Where can I learn more about the mathematics behind this assessment? The Assessing Math Concept series by Kathy Richardson contains important information for educators. It is recommended that teachers read the following information from Two-Digit Addition & Subtraction Concept 9. Learning to Count Example of Student Interview Grade Level Expectations Assessing Children at Work Linking Assessment to Instruction

Overview of Two-Digit Addition & Subtraction Assessment Present a variety of two-digit problems to student: Solves Problem with Model – showing trains of cubes Solves Problem w/out Model – cover cubes with paper Solving Symbolic Problems – use equation cards Assessment is capturing student’s answers, their strategies for solving the problems and their use of the models. Equation Cards available in the Downloads section of

What are the choices for strategies during the Two-Digit Addition & Subtraction Assessment? Knows parts to make/adds ten: Student easily forms tens; knows parts of numbers without having to figure anything out. Counts to make/add ten: Student can form tens and leftovers, but not automatically and still needs to figure them out. Visualizes written problem: Trying to solve problem using standard algorithm. Counts all or on: Student still thinks of numbers as a collection of units (rather than tens & ones) and counts all or on to get answer. Strategy Unknown: Prompts teacher to ask “How did you think about that?”

Assessment Results Summarized at end of assessment as: A – Ready to Apply P – Needs Practice I – Needs Instruction Complete descriptions included in assessment guide.

Use AMC Anywhere reporting to view student results. Interpreting & Using Assessment Results Select Reports Select from a variety of reports.

Use “Linking Assessment to Instruction” guides for instructional support from Developing Number Concepts Select Downloads Select Linking Assessment