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The Abridged Math Tools for Journalists: Wickham Briefing chpts. 9-12

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Directional Measurements

         Directional measurements are things like time, rate and distance, and are necessary to journalism. When working with time, rate and distance, you have to make sure the units stay the same. The formula involving these three things is: Distance = rate x time. This can be rearranged also as Rate = distance/time and Time = distance/rate.

Example 1

A train is approaching a station at 70 mph, and is 200 miles from the station. When will the train arrive at the station? 

Time= 200/70

Time = 2.9 hours 

Other directional measurements are speed, velocity, acceleration, g-force and momentum. Be careful not to get speed and velocity confused. Speed measures how fast something is going where as velocity also indicates its direction. Most reporters will only have to figure out speed. The most useful formula for speed is average speed, which is calculated by dividing distance by time. Acceleration is also useful to find out. The formula is acceleration = (ending velocity – starting velocity) / time. To come up with ending velocity for a free falling object, you can plug 9.8 meters/second into the acceleration formula. But if you only know the distance it fell, you can use the formula ending speed = square root of (2(acceleration x distance)). One last measurement is momentum, determined by mass x velocity.

Area Measurements

Area measurements can often by done through visual analogies by journalists, but sometimes the reader might not understand the analogy, and that is where numbers come in. Analogies also fail to give exact numbers. Following are basic formulas for all areas of measurement.

Perimeter = (2 x length) + (2 x width)

Area = length x width

Area of a triangle = .5 base x height

Circumference = 2p x radius

Example 2 

A reporter wants to find out the circumference of a trampoline. The distance from one end of the trampoline to the other is 10 feet. 

Circumference = 2pi x 5

Circumference = 31.4 feet 

If you wanted to later find the area of a circle, you would use the formula Area = pi x radius^2.

Volume Measurements 

            Volume measurements are also essential to journalism. To understand liquid measurements, journalists must know common liquid conversions. For example, 16 ounces equal 1 cup and 4 quarts equal 1 gallon. To find the volume of a rectangular solid, use the formula Volume = length x width x height.

Example 3 

What is the volume of a treasure chest measuring 7 inches long, 4 inches wide, and 3 inches tall? 

Volume = 7 x 4 x 3

Volume = 84 cubic inches 

One last measurement is the ton. There are different types of tons: a short ton (2000 pounds), a long or British ton (2240 pounds) and a metric ton (1,000 kilograms or 2204.62 pounds).

The Metric System 

Even though it is not commonly used in America, it is very important that journalists understand the metric system, especially if they are dealing with international commerce. The metric system is based on multiples of ten and the decimal system. Users can change from one unit to another by multiplying or dividing by multiples of ten. Unit names are meter (length), gram (mass) and liter (volume). These are changed to make greater or smaller numbers by adding prefixes like kilo, centi, mili. When it comes to length, to change from American lengths to the metric system, there are set conversions:

–       inches by 25.4 for millimeters or 2.5 for centimeters

–       feet by 30 for centimeters or .3 for meters

–       yards by 90 for centimeters or .9 for meters

–       miles by 1.6 for kilometers

Example 4 

The length of garden tract was 50 feet. The requirements for the tract were 20 meters. Did the tract meet the requirements? If not, how long would the tract have to be in feet? 

50 feet x 0.3 = 15 meters

No, it did not meet the requirements.  So use the formula to determine length in feet. 

Length x .03 = 20

Length = 20/.03

Length = 66.67 feet 

Style points:

–       All units are lower case

–       Units are plural only when the numerical value that precedes them is more than 1

–       Symbols are never pluralized

–       A space is used between the number and the symbol it refers to

–       Periods are not used after unit names, unless at the end of a sentence

[All credit goes to Kathleen Woodruff Wickham]

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Written by juliasayers

May 6, 2011 at 9:36 am

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