CONTENT & PROCESS SKILLS
Reasonableness of Solutions
The Right Units/Dimensional Analysis
The Right Size
The Right Picture-Graphs & Diagrams



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Judging the reasonableness of solutions has proved to be one of the most challenging mathematics skills for elementary students in the Houston Independent School District. The SMI staff believe that students need manipulatives and other kinesthetic experiences that require quantitative measurements to develop this skill. The following are some other activities that are useful for judging the reasonableness of solutions.

The Right Units/Dimensional Analysis

Encourage students to always include the units of their data and check to be sure that the units are reasonable. A person's weight should be pounds or Newtons; not inches, square meters, or decibels. A student who is using a measurement tool to collect the data will associate the appropriate units with the physical attribute. When calculating measurements using more than one kind of data, have them check for the reasonableness of the units in their answers. For instance, a reasonable unit for walking speed is meters/second, not just meters or seconds.

Dimensional analysis is a good way to check to see if your answer is reasonable when you are calculating problems with multiple types of units. For more information about dimensional analysis, you may wish to consult a chemistry teacher a nearby high school, or visit this web site:
Chemistry Tutor: Factor-label Method


The Right Size

The development of the concept of place value is important for students to acquire in their early elementary years. Manipulative experiences help children appreciate how different one, ten, and a hundred are. Math manipulatives are also useful for students to correct their own errors.

Check Yourself
Rewrite these numbers from the smallest to the largest:
Answer

For more information about how many significant digits your answers should have, visit this web site:
Chemistry Tutor: Significant Digits


The Right Picture-Charts, Graphs, & Diagrams

When you ask your students to organize and graph data they collect in laboratory work, you have the opportunity to check on their mastery of a variety of skills and knowledge. Don't always give them charts and graph axes that are already labeled. Even though it takes extra time correcting idiosyncratic data sheets, it is important for students to be required to make decisions such as:



  • Which variable should be on each axis?
  • What units should be used for each axis?
  • What unit scale should be used?
  • What kind of graph should be used---bar, line, or scatter plot?

Check Yourself
Why doesn't the distance the car is traveling increase after 3 seconds?
Answer

Time
(seconds)

Total Distance Car Traveled
(cm)

0
0
1
50
2
75
3
80
4
80


This page was last updated 04/10/01.
Web Page Author: Debbie Jensen djensen@rice.edu
The SMI Teacher Enhancement Web Site
is part of the Rice University Precollege Web Site
Web Site Master: Marty Daniel martyd@rice.edu