What This Means for Instruction

Here are some tips to help educators plan instruction on estimation:

• Model for students and instruct them in how to determine whether a particular situation requires an exact answer or an estimate, and the degree of accuracy needed.
• Model for students how you estimate the answers to various problems you encounter in your daily life and in the classroom.
• Model various estimation strategies such as:
• flexible rounding
• using benchmarks
• front-end strategies
• Provide ample opportunities for students to estimate and to share and compare their methods.
• Allow students to develop their understandings by inventing their own methods to estimate and compute. Later, have them employ the strategies listed in Ohio's Academic Content Standards for mathematics.
• Invite students to reflect on predicted solutions and explain their thinking.
• Shift students' attitudes and help them recognize the benefits of estimates. Most students believe that an exact answer is better than an estimate (Sowder & Wheeler, 1989); whereas good estimators appreciate the usefulness of estimation and are less concerned with being precise (Reys, Rybolt, Bestgen, & Wyatt, 1982).
• Provide explicit instruction in the strategies used by successful estimators:
• Reformulation - Changing numbers to other numbers that would be easier to use
• Translation - Changing the structure of a problem so it would be easier to do in one's head
• Compensation - Making adjustments before and after estimating (Reys, Rybolt, Bestgen & Wyatt, 1982)
• The Southern Regional Education Board provides the following suggestions for activities involving estimation:
• Ask students to identify large quantities to be estimated (such as the number of shingles on a roof or the number of leaves on a tree). Have them discuss their estimation strategies and solutions.
• Invite students to develop mental strategies for calculating the tax or tip and compare their methods with their classmates.

(Getting Students Ready for Algebra I: What Middle Grades Students Need to Know and Be Able to Do, 2002).