When it comes to teaching students estimation, the teacher's first priority is to inform the students what the basic concept of estimation is.  The teacher begins this  process by aiding the students in developing a tolerance for error.  Students beginning estimation may encounter difficulties because "exact" answers will not be obtained.  Students need teacher guidance in assisting them to become more accepting to the "close but not exact" answers (Heimer & Trueblood, 1977).

Many times teachers and other professionals may raise the question, "When do the students grow out of the "exact answer" mentality"?  Reys, Suydam, and Lindquist report this change will begin when the students recognize estimation as an essential and practical skill in mathematics.  As elementary school teachers, we must emphasize computational estimation and exact answers within different problem situations. Teacher/student discussions, and various activities aid in reducing the belief  estimation is "inadequate" or not as good as an exact answer (Heimer, et al., 1977).

When students develop an awareness of the uses for estimation, they become familiar to when and where to estimate.  Conversely, it is crucial students are provided essential skills that involve an understanding of number sense and a greater appreciation of estimating.  Once this mathematical landmark is attained, instruction on the basic and powerful notions of estimation can begin (Heimer, et al., 1977). 

Focusing on Front-End Digits
Front-end strategies are basic, yet a powerful approach that can be used in a variety of situations.  Two important concepts must be addressed: (1) the leading or front-end digit of a number (2) place value of those digits.  Instead of tedious algorithms for exact answers, an estimate provides an answer efficiently by focusing on front-end numbers (Heimer, et al., 1977). 

For example: By looking at the first digit in each amount, a person can estimate about how much lunch will cost.  Grill cheese: $2.15 and Chips $1.25.  With a $5 bill, do you think there is enough money to purchase the items? 

"students must have an idea of number sense in order to teach fact strategies"