Estimation and Significant Figures

Dick Trent Elk Grove High School
500 W. Elk Grove Blvd.
Elk Grove Village, IL 60007


(This activity is intended for high school students)
This activity will aid the student in understanding the estimation of
measurements and the use of significant figures in measurement and calculations.

Materials needed (for each lab group):

Pieces of construction paper cut to various sizes
(possible lengths: 67mm, 27mm, 137mm, 47mm)
Ruler calibrated to millimeters
Ruler calibrated to centimeters
Ruler calibrated to decimeters


This is a simple activity which is used in the beginning of the year. It
can be used in physical science, chemistry or lower level science and math
classes. Give each group a package consisting of a group of four pieces of
paper. Tell each group to measure the pieces of paper with each of their rulers
and make a data table which shows paper number and ruler used. Label this table
"individual paper table". The length of the paper should be rounded to the
nearest marking on the ruler. Then have the students lay the pieces of paper
side by side and measure the length of the entire string with each of the rulers
and make a table labeled "paper string table". The students should add up the
length of each individual piece to get a "theoretical" total length using the
data from "individual paper table" for each separate ruler.
Discussion following this activity should focus on the comparison between
the theoretical total length and the measured total length. Questions which
might be posed include "Did the papers change length?" and "When converted to
meters, what is the relationship between the different rulers?" The students
should discuss the principles behind the need for significant figures in order
to get accurate totals when using measuring devices with different calibrations.
An analogy that explains this concept is one with money. If a person who
only has dollar bills were to go into a store that does not give change and
purchase an article that is priced at $0.75, the person would lose $0.25. If
the person did this four times, they would have paid $4 for articles worth $3.
They would have lost a dollar. This shows how rounding and estimation are
important concepts to understand. This also explains why stock prices are given
to such precision.
This type of project can be modified for younger students in order to
display the same concepts of estimation, rounding and significant figures. The
rulers can be made out of laminated poster board or pre-made rulers with the
markings taped over and remarked to the correct units.

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