An overview of Kathleen Wickham’s ‘Math Tools for Journalists,’ chapters 9–12

Chapter 9: directional measurements

Reporters shouldn’t simply rely on numbers provided by people involved in a story. Checking the numbers in time, rate and distance problems usually involves just some basic math.

In time, rate and distance problems, the basic formula is the same, but components are switched around depending on the solution needed.

Distance = rate * time

Rate = distance / time

Time = distance / rate

Speed and velocity are not the same measurement. Speed measures how fast something is going, while velocity indicates its direction.

The speedometer on a car gives the driver the speed at exactly one moment. This is called instantaneous speed. A more useful figure for a reporter is average speed, which is calculated by dividing the distance traveled by the time it took to get there.

Average speed = distance / time

Acceleration = (ending velocity – starting velocity) / time

Therefore:

Ending velocity = (acceleration * time) + starting velocity

Mass is a measure of amount. Weight is a measure of the force of gravity pulling an object. Mass is the same regardless of gravity.

To determine the speed of an object when it hits the ground. One needs to manipulate the equation for acceleration.

Ending speed = √2(acceleration * distance)

Momentum is the force necessary to stop and object from moving.

Momentum = mass * velocity

Practice problem

Janet Adamson is writing about the speed of a train, which commonly passes through Elrond University’s campus. The train’s acceleration at full throttle is .3 miles per hour per second. If the train is already moving 30 mph, and accelerating at full throttle for 3 minutes, how fast will it be going?

Chapter 10: area measurement

Knowing how to express measurements in an accurate and clear way is vital to good journalism. Analogies are a great way for illustrating measurements that may be otherwise meaningless, but analogies sometimes fail when exact measurements are essential.

Premature of a rectangle           

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

Area of a rectangle

Area = length * width

Area of a triangle

Area = .5 base * height

Small spaces are measured in square inches or square feet. Larger areas, such as parking lots, are measured in square feet, square yards or square rods.

144 inches = 1 square foot

9 square feet = 1 square yard

30 square yards = 1 square rod

160 square rods = 1 acre

1 acre = 43,560

640 = 1 square mile

The radius of a circle is the distance from any edge to the middle. Knowing the radius is key to finding the circumference, or the distance around. Knowing the radius is also necessary to find the area of a circle.

Circumference = 2Pi * radius

Area = Pi * radius2

Practice problem

Elrond University’s quidditch field is 120 yards long with two end zones of 5 yards each and a width of 75 yards. What is the field’s parameter and area?

Chapter 11: volume measurements

Volume measurements play a key role in many articles, especially on the business beat.

Rectangular solid

Volume = length * width * height

Common liquid conversion

2 tablespoons = 1 fluid ounce

½ pint = 8 ounces, or 1 cup

1 pint = 16 ounces, or two cups

2 pints (32 ounces) = 1 quart

2 quarts (64 ounces) = ½ gallon

4 quarts (128 ounces) = 1 gallon

1 U.S. standard barrel = 31.5 gallons

1 U.S. gallon = 4/5 Imperial gallon

British or Canadian barrel = 36 Imperial gallons

Cord

A cord is commonly used to measure firewood, and is defined as 128 cubic feet.

Ton           

There are three different types of tons. A short ton is 2000 pounds. The British ton is the long ton, which is 2240 pounds. There is also a third type of ton called the metric ton, equal to 1000 kilograms, or 2204.62 pounds.

Practice problem

A famous book of college reviews sent one of their workers to Elrond University to measure the size of a student dorm room. The rectangular room is 8 feet by 12 feet by 12 feet. How many cubic feet is the dorm room?

Chapter 12: the metric system

Outside the United States, most of the world uses the metric system for nearly every type of measurement. The unit names are meter (length), gram (mass) and liter (volume).

Length (metric) U.S.
1 millimeter [mm] 0.03937 in
1 centimeter [cm] 10 mm 0.3937 in
1 meter [m] 100 cm 1.0936 yd
1 kilometer [km] 1000 m 0.6214 mile
Area (metric) U.S.
1 sq cm [cm2] 100 mm2 0.1550 in2
1 sq m [m2] 10,000 cm2 1.1960 yd2
1 hectare [ha] 10,000 m2 2.4711 acres
1 sq km [km2] 100 ha 0.3861 mile2
Volume/ Capacity (metric) U.S.
1 cu cm [cm3] 0.0610 in3
1 cu decimeter [dm3] 1,000 cm3 0.0353 ft3
1 cu meter [m3] 1,000 dm3 1.3080 yd3
1 liter [l] 1 dm3 2.113 fluid pt
Mass (metric)   U.S.
1 milligram [mg] 0.0154 grain
1 gram [g] 1,000 mg 0.0353 oz
1 kilogram [kg] 1,000 g 2.2046 lb

Temperature

(1.8 * °C ) + 32 = °F

.56 * (°F – 32) = °C

Practice problem

 While studying abroad, Janet Adamson was asked to cook her host family dinner. She needs approximately 3 pounds of flower to bake dessert. Will a 1 kg bag be enough? Why or why not?

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