A Reasonable Estimate

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Updated on Mar 19, 2013

Grade Level: 7th;Type: Physical Science


Determine how proficient you are at making estimations and learn how to make more reasonable estimates.


On a skills level in the science lab as well as in daily life being able to make reasonable estimates is a process worth developing. In our rapid pace of living, we frequently are required to make estimates rather than undergoing time consuming computations. There are times when we make an estimate as a time saver and hope that our approximation will serve our purpose. In many fields of science, we are at times unable to make direct measurements and so we rely on estimating based on our previous experience with the phenomena with which we are dealing. In mathematics, approximation, another term for estimating is interpreted as finding upper or lower limits of a quantity that we cannot compute precisely. Another example, in Physics, a Fermi problem is defined as one which typically involve making justified guesses about quantities that seem impossible to compute given limited information? In sum, indirect measurement, namely, estimating is a very essential skill be it in the science laboratories or in life`s daily experiences. Few of us are aware of how often , be it in driving a car or running a lawn mower, we do make estimates with little thought about the process. Nor do we fail to recognize how proficient we have become in making rather accurate estimates!

Research Questions

  • What is direct measurement?
  • Provide 3 examples of direct measurement that we employ on a daily basis.
  • What is indirect measurement?
  • Provide 3 examples of indirect measurements we make on a daily basis.
  • What are some of the advantages of direct measurement?
  • What are some of the disadvantages of direct measurement?
  • What are some of the advantages of estimating?
  • Under what kinds of conditions are we justified in using estimation?
  • Under what conditions, would it be dangerous to use indirect measurement?
  • In what instances during the day might we use estimation without giving it much thought?

Terms to Know

  • Direct measurement
  • Indirect measurement
  • Estimation
  • Estimation theory


  • 10 pennies
  • Jar of beans
  • Metric ruler
  • Meter stick
  • 25 rubber bands
  • Piece of paper
  • Stack of 30 sheets of paper
  • Watch with a second hand
  • Camera

Experimental Procedure

  1. Gather all the materials that you will need for your project. 10 pennies, a jar of beans, a metric ruler, a meter stick, a box of rubber bands, a piece of paper, a ream of 500 sheets of the same paper, a watch with a second hand. You may wish to include a camera and take photos of the steps taken and the obtained results.
  2. Copy the Data Summary Chart provided below so that you can readily record your observations.
  3. Start with the jar of beans and estimate the total number of beans in the jar. Record your estimate on the Data Chart.
  4. Now count the number of beans on the bottom of the jar and the number on the side from top to bottom. Using this data estimate the total number of beans in the jar. Record on the data chart.
  5. Now count the number of beans in the jar and record the data.
  6. Start with the piece of paper. Now your task is to estimate the thickness of the sheet of paper. Record your estimate. Now continue, by measuring the thickness of the ream of paper and dividing that number by 500 to get the actual thickness of just one sheet. Record your answer.
  7. Now keeping in mind what you did with the paper, you are now taking the rubber band. You are to determine the mass of a rubber band. How can you use the box of 100 rubber bands to estimate the mass of one rubber band? Record what you would do on your data sheet.
  8. This time you will estimate how long it takes for one minute to go by. Ask someone to help you. Tell your helper when you think a minute has passed and have him or her tell you how much time actually went by. Record your data.
  9. It is pulse time! Use your watch and measure how many times your pulse beats in 30 second. Record your pulse beat number. Now with the assistance of your helper,
  10. use your pulse count to estimate one minute. Record your answer. How close did you get?
  11. The task now is to estimate the mass of a penny. Take a guess! How many grams? Record your guess. The mass of a nickel is 5 grams. Estimate how many pennies have the same mass as the nickel. Record your answer. Review all the estimates you made.
  12. Think about it! How could you have improved your estimation process?
  13. Think about other measurements such as the distance to the closest star. How is that measurement made? Include that information in your report.
  14. Write up your project. You may wish to include photos. Be certain to include your bibliography. Becoming a good estimator may be challenging! Was it in your project?

Data Summary Chart



Actual Measurements

Jar of Beans

Thickness of Paper

Mass of Rubber Band

Pulse Beats

Mass of Penny


  • Johnson, Gordon, Barr, Bonnie, Leyden, Michael, Physical Science, Addison-Wesley New York, 1988.
Dr. Muriel Gerhard (Ed.D.) is a retired educator with fifty seven years of experience in all aspects of public education. She has been a teacher, principal, administrator, college professor, researcher, grants writer, change agent and science editor. She is the author of several books on education used as college texts. These include the best selling Effective Teaching Strategies with the Behavioral Outcomes Approach and The Behavioral Outcomes Handbook for Teachers and Administrators. Presently she is a consultant in science education and curriculum development, a marriage and family therapist, a newspaper columnist and an author. Her latest book, recently published, is a memoir of sixty vignettes entitled âNow That I`m Dead, I Decided to Write this Bookâ.

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