ESTIMATING

RESEARCH FINDING:

Although  students  need  to learn how to find exact  answers  to 
arithmetic  problems,  good math students also learn the  helpful 
skill of estimating answers.  This skill can be taught.

COMMENT:

Many people can tell almost immediately when a total seems  right 
or  wrong.   They may not realize it,  but they are using a  math 
skill called estimating.

Estimating can also be valuable to children learning math.  

When students can make good estimates of the answer to an  arith-
metic problem,  it shows they understand the problem.  This skill 
leads  them  to reject unreasonable answers and to  know  whether 
they are "in the ballpark."

Research  has identified three key steps used by good estimators; 
these can be taught to all students:

   . Good estimators begin by altering numbers to more man-
     ageable forms--by rounding, for example.

   . They change parts of a problem into forms they can handle
     more easily.  In a problem with several steps, they may rearrange 
     the steps to make estimation easier.

   . They also adjust two numbers at a time when making their
     estimates.  Rounding one number higher and one number lower is an 
     example of this technique.

Before students can become good at estimating,  they need to have 
quick,  accurate  recall of basic facts.   They also need a  good 
grasp of the place value system (ones, tens, hundreds, etc.). 

Estimating  is a practical skill;  for example,  it comes in very 
handy when shopping.   It can also help students in many areas of 
mathematics and science that they will study in the future. 


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struction  on  Attitudes and Computational Estimation  Skills  of 
Preservice Elementary Teachers."  Journal for Research in  Mathe-
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Reed,  S.  K.  (l984).  "Estimating Answers to Algebra Word Prob-
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Cognition, Vol. l0, pp. 778-790.

Reys,  R.,  et al. (l982).  "Processes Used by Good Computational 
Estimators."  Journal for Research in Mathematics Education, Vol. 
13, pp. l83-20l.

Schoen,  H.  L., et al. (l98l).  "Instruction in Estimating Solu-
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Mathematics Education, Vol. 12, pp. 165-178. 

Trafton,  P.  R. (l978).  "Estimation and Mental Arithmetic:  Im-
portant  Components of Computation."  In Developing Computational 
Skills, l978 Yearbook.  Reston, VA:  National Council of Teachers 
of Mathematics.