Domain

Measurement and Data

Operations and Algebraic Thinking

Cluster

Relate addition and subtraction to length.

Represent and solve problems involving addition & subtraction.

Standard(s)

NC.2.MD.6 Represent whole numbers as lengths from 0 on a number line diagram with equally spaced points and represent whole-number sums and differences, within 100, on a number line.

NC.2.OA.1 Represent and solve addition and subtraction word problems, within 100, with unknowns in all positions, by using representations and equations with a symbol for the unknown number to represent the problem, when solving:

•  One-Step problems:

o (continued from 1st grade) Compare-Difference Unknown

Materials

SF, pencil

Task

Provide materials to the student. Read the problem to the student: The 2nd graders had a jumping contest. Mary jumped 38 inches. Sue jumped 55 inches. How much farther did Sue jump than Mary? Use a number line to solve. Use numbers and words to show your thinking.

Continuum of Understanding

Not Yet Proficient

·         Provide conceptual instruction on making sense of the situation as a comparison difference unknown problem

·         Provide procedural instruction on solving comparison difference unknown problems

·      Provide instruction on place value when adding and subtracting with regrouping

·      Provide instruction on accurately drawing a number line

q  Draws and uses a number line as a tool to solve the problem accurately.

q  Solves the problem correctly

q  Clearly explains their thinking

Strategy(ies) Used:

q  Counting On

q  Counting Back

q  Makes Tens

q  Creates easier or known sums

q  Basic Facts

q  Doubles

q  Doubles +/- 1, 2

q  Other:

Progressing

·      Attempts to draw a number line but is unable to represent spaces accurately.

·      Solves the problem incorrectly.

·      Draws the number line inaccurately.

·      Justification is weak and/or does not accurately represent the strategy used on the number line.

Meets Expectation

·      Correctly solves the problem: 17 inches

·      Represents numbers as lengths on a number line with equally spaced points corresponding to necessary numbers.

·      Uses the number line as a tool to solve the problem accurately.

·      The justification is clear and uses numbers, pictures, or words to show their thinking.

·      The justification accurately represents the strategy used on the number line