Length Indirect Comparer
Sub Trajectory: Non-Measurement Comparison

Compares the length of two objects by representing them with a third object. Uses terms: long, longer, longest, short, shorter, shortest. When asked to measure, may assign a length by guessing or moving along a length while counting (without equal-length units). May be able to measure with a ruler, but often lacks understanding or skill (e.g., ignores starting point).


You may see this:

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Other Examples:

  • Compares length of two objects with a piece of string. 
  • Moves finger along a line segment, saying, "10, 20, 30, 31, 32."  
  • Measures two objects with a ruler to check if they are the same length, but does not accurately set the "zero point" for one of the items. 

Help your student become a(n) Length Indirect Comparer

Activities are carefully planned to make the (easier!) direct instruction difficult or impossible, so children are challenged to use a third object (e.g., a piece of string) to compare two others (e.g., width of a heavy table and a doorway). Discussion focuses on transitive inference--if A is longer than B and B is longer than C, then A is longer than C.

Special Thanks To

Institute of Education Sciences
The research reported here was supported by the Institute of Education Sciences, U.S. Department of Education, through grant numbers R305K050157, R305A120813, R305A110188, and R305A150243. to the University of Denver. The opinions expressed are those of the authors and do not represent views of the Institute or the U.S. Department of Education.