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Browse Middle School Measurement
Stars indicate particularly interesting answers or good places to begin browsing.

See also:
      Terms/Units of Measurement

Selected answers to common questions:
    A million/billion seconds.
    Significant figures/digits.
    Unit conversions, unit cancellation.
    Using a protractor, reading a ruler.

4- and 9-liter Pails: How to Measure 7 Liters [05/07/2002]
How can you measure 7 liters using only 4-liter and 9-liter pails? A strategy for solving this kind of problem.

Administering Insulin [07/09/2003]
If a doctor prescribes 30 units of insulin in 500 ml to be administered over 2 hours, how many drops per minute should be administered if the set is calibrated to deliver 20 drops per ml?

Groups and Units: Multiply or Divide? [04/15/2003]
Changing units to other units.

Measurement: Precision vs. Accuracy [01/07/2003]
Using a metric ruler student A measured the length of an object to the nearest tenth (0.1) of a centimeter, while student D measured its length to the nearest centimeter. Which measurement is more accurate?

Measuring Material [07/04/2003]
I need 225 4-inch squares cut from cotton material. If the material is 30 inches wide, how many yards of material will I need?

Operations on Measurement Units [08/21/1998]
Why can we divide distance by time, but not add distance to time?

Reading a Ruler [09/18/1997]
I need to read a ruler, and I can't. Can you help me?

Unit Analysis and Conversion Factors [02/01/2003]
How to convert the following? 7.5 x 10^4 nm to kilometers; 3.9 x 10^5 mg to decigrams; 2.21 x 10^-4 dL to microliters.

Volume to be Infused by Drip Factor [07/02/2003]
A patient is to receive 1440 milliliters of fluid in 24 hours. The drip factor is 15 drops per milliliter. How many drops per minute should the patient receive?

What is a Significant Digit? [12/25/2001]
I came across a question asking for an answer with no more than "2 significant digits" - can you please explain what a significant digit is?

What is a slide rule? [07/27/1997]
What does a slide rule do and how does it work?

2 Square Feet vs. 2 Feet Square [11/22/1998]
What is the difference between 2 square feet and 2 feet square?

About Measurements and Unit Conversion [02/03/2002]
I don't understand measurements.

Accuracy in Measurement [02/08/2002]
Since pi is irrational, either the circumference or the diameter of a circle must be irrational. How is that possible?

Accuracy in Measurement [01/09/2007]
I've heard that it's impossible to measure things exactly, and I don't understand that. How can our world be based on estimations?

Analyzing a Prescription for the Correct Dose [04/27/2005]
A 46 lb child is prescribed 1 Tsp of medicinal syrup three times a day. There are 2 mg of medicine per 5 ml of syrup, and a safe dose is 0.1 mg per kg of body weight. Is the prescribed dose safe?

Benchmarks [03/25/2001]
What is a benchmark? Could you please give me an example?

Calculating Errors in Measurement [08/06/2002]
Suppose you are told that a digital scale measures to the nearest 0.2kg and asked to find the absolute error involved in using the scale to weigh a cat that weighs 7.4 kg.

Changing Units ... and Significant Figures? [08/22/2011]
A student seeks clarity with the significant digits required after converting a measurement from US customary units to metric. Reinforcing how precision applies to measured data, Doctor Peterson walks through an example.

Choosing a Unit of Measurement [05/06/2002]
What's the proper unit of measurement for measuring butterflies?

Comparing Volume and Surface Area [05/01/2002]
Why is it that the surface area of a given rectangular solid can sometimes be greater than the volume of that solid?

Complementary or Supplementary? [04/02/2001]
I keep getting complementary and supplementary mixed up. How can I remember which is which?

Converting Grams to Milliliters [05/12/2006]
How many milliliters would 35 grams of flour fill?

Converting Metric Measurements [11/03/2005]
I don't understand how to convert 50 millimeters into centimeters. Do I multiply 50 by 10 or divide it by 10? How do I decide?

Converting Millimeters to Inches and Back [03/14/2003]
I would like to see how to calculate without a chart.

Converting Units across Measurements [08/31/2010]
How do you convert units to a different measurement? And how do you know how many decimal places to move as a result? Doctor Ian suggests making the multiplication of units explicit, and introduces ratios of two quantities equal to each other.

Converting Units of Measure [7/17/1996]
Find the unit of measure for (3 pounds over 1 square inch) * (144 square inches over 1 square foot)....

Cutting Equal Strips [09/08/2005]
Given five 4 ft by 8 ft rectangular sheets of plywood, how many strips that are 7 1/2 inches wide and 8 feet long could you cut? Each saw cut eliminates 1/16 inch of the plywood as sawdust, and you are not able to glue any strips together.

Defining Counts [07/05/2016]
An adult struggles to disambiguate a unit label from the variable that represents the amount of that unit. Doctor Peterson clears up the confusion before reconciling the different uses with explicit labeling and dimensional analysis.

Dimensional Analysis and Unit Conversions [09/15/2002]
Using dimensional analysis, convert 8 feet/second to kilometers/hour.

Does Pi Equal 3.14? [01/27/1998]
We use pi as 3.14. How can this be right?

Exact Numbers and Conversion Statements [07/25/2005]
I'm confused about how to decide if a number is exact or inexact. I know that in general measurements are considered inexact, but how about conversion factors such as 1 inch = 2.54 cm? The exactness of the number plays a role in the number of significant digits to keep. What other kinds of numbers are considered exact and inexact?

Explanation of Significant Figures [09/11/2007]
I'm confused about how to determine how many significant digits a given number has. Can you explain it?

Feet Per Second [02/22/2003]
Determine the velocity in a pipe in ft. per second... Where does the constant term in the formula come from?

Fraction or Decimal? [06/23/1998]
Which is more precise, a fraction or a decimal - for instance, 1/3 or 0.33?

Fundamental Idea of Division [03/24/2000]
My 8-year-old daughter had 12 bracelets which she arranged into 4 piles of 3. Did she divide 12 by 3 or by 4?

How Many Blocks in a Mile? [11/24/2005]
How many city blocks are there in a mile?

How to Calculate Greatest Possible Error [04/12/2004]
I'm an 8th grade student working on greatest possible error and it just doesn't seem to make any sense. I know that GPE is half of the smallest unit of measure, but I don't understand how to decide what the smallest unit of measure is.

Inches and Feet and Miles, Oh My! [04/14/2008]
Why are English measures inconsistent in conversions? The metric system works in the meter and power of tens, but English units are kind of crazy (1 ft = 12 in, 3 ft = 1 yd, 1 mi = 1760 yd or 5280 ft, etc.).

Indirect Measurements and Hubble's Constant [01/31/2003]
How are indirect measurements used in astronomy? For example, how can scientists tell how far the Earth is from Pluto?

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