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Understand unit analysis (or dimensional analysis) through conversion examples. Learn how to convert units for different measurements with practical scenarios. Enhance your math skills with this detailed guide.
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UnitAnalysisSupplementto Math 60Chapter 3 Cathy Mulleary Summer 2013
Unit Analysis Alternate names for the same process are: • Unit Conversions • Factor Label Method • Unit Factor Method • Dimensional Analysis
Unit analysis uses the same concept as “equivalent fractions.” Multiplying a quantity by a ratio equal to one changes the looks of the quantity without changing its value.
The process of unit analysis focuses on converting to the units necessary to answer a question. Example: How many feet are there in 360 inches? In order to answer the question, I need to know a “conversion fact.” In this case, the fact is: 1 foot = 12 inches. Start with the value we are “converting” (writing it as a fraction is VERY helpful). Always include the units. This is required. Next, multiply the starting value by the conversion fact written as a fraction. Now, it’s just arithmetic.
The question is: How do I know how to write the conversion fact? What goes on top? What goes on the bottom? • You must arrange the conversion fact so the units “drop out.” • In the previous example, reversing the top and bottom wouldn’t work because the units don’t get eliminated.
Example: How many centimeters are there in 23 feet? The conversion facts needed are: 1 in = 2.54 cm 1 ft = 12 in Choosing the right conversion facts requires you to “figure out” how am I going to get from cm to ft with the conversions facts I know or have available. Note: It is NOT acceptable for you to look up a conversion; although they are readily available on the internet. You to be able to figure it out knowing just a few facts.
Example: Rewrite 3521 mL as quarts. The conversion facts needed are: 1tsp = 5mL 1c = 48tsp 4c = 1qt Rounded to the hundredths place this is 3.67 qt.
Last example: Convert 60 mph to kilometers per hour; round to the nearest hundredth. Conversion facts needed 1mi=1760yd Kmph is a common abbreviation for
Now you try: Katelyn can bicycle at a rate of 100 yards in 15 seconds, what is her rate in miles per hour? (round to the nearest tenth) Necessary conversions: 1mi = 1760yd 1min = 60sec 1hr = 60min = 13.6 mph