Math Tools for Journalists: Measurements
By Kate Austin
DIRECTIONAL MEASUREMENTS
Many news stories include directional measurements that are vital to readers and should be checked by journalists by using basic math.
“The challenge here is to be able to check the work of officials, and to do it with confidence. The result is greater accuracy for the reader or viewer, which is what is important in journalism – not to be first, but to be first with what is right.” – Math Tools for Journalists, Second Edition, Kathleen Woodruff Wickham
Time, rate and distance problems:
Be sure to keep the units of measurement the same: if the rate is in miles per hour, then the time needs to be in hours and the distance in miles.
Formulas:
Distance = rate x time
Rate = distance / time
Time = distance / rate
Sample Problem:
Billy Maxwell, a reporter for the Yellow Yellowstonian, was sent to the state capital to cover a free-trade discussion. If he drove 70 mph on the interstate for 9 hours, how far did he travel?
Answer: Distance = 70mph x 9 hrs = 630 miles
Speed, velocity, acceleration, g-force and momentum:
Speed: Measures how fast something is going
Velocity: Measures how fast something is going and also indicates its direction.
Average speed: calculated by dividing the distance traveled by the time it took to get there
Formulas:
Average speed = distance / time
Acceleration = (ending velocity – starting velocity) / time
Ending velocity = (Acceleration x time) + starting velocity
G-force: an acceleration measure. One “g” represents the normal force of gravity on the Earth’s surface
To determine the speed an object was at when it hit the ground, you need the ending speed formula.
Formula: Ending speed = √ 2(acceleration x distance)
Momentum: The force necessary to stoop an object from moving.
Formula: Momentum = mass x velocity
AREA MEASUREMENTS
There are two ways to explain measurements: analogies or with numbers. Analogies, like “The casino is the size of a football field,” are great for illustrating measurements that may be otherwise meaningless. When it is easier for a person to picture a size in comparison to something they already know the size of rather than hear a specific number and try to imagine it, analogies are best. It is important that you use analogies that your readers will easily understand.
Perimeter: The outside measurement of a square or rectangle
Formula: Perimeter (of a square/rectangle) = (2 x length) + (2 x width)
*If the object has an irregular shape, add the lengths of all sides to find perimeter.
Area of squares and rectangles
Formula: area = length x width
Area of a triangle:
Formula: area = 0.5 base x height (use the two shortest sides as base and height)
Square feet, square yards: Larger areas are measured in square feet, square yards, or square rods.
Radius: the radius of a circle is the distance from any edge to the middle
Circumference: the distance around a circle
Formula: Circumference = 2∏ x radius
Formula: Area (of a circle) = ∏ x radius^2
Sample Problem:
Robin, a reporter for the Hen’s Holler, wants to know the distance around a round flower garden at Tweeter Park. The distance from the edge of the garden to the middle is 15 feet.
Answer: 2∏ x 15 = 94.2 feet
VOLUME MEASUREMENTS
Liquid Measurements apply to liquids in recipes, bodies of water and other fluids.
Rectangular solid:
Formula: Volume = length x width x height
Cord: Firewood is sold by a measurement called a cord, or 128 cubic feet when the wood is neatly stacked in a line or row. A standard cord would be a stack of wood 8 feet long, 4 feet wide and 4 feet high.
Ton: There are different types of tons:
• A short ton is equal to 2,000 pounds
• A long ton, also know as a British ton, is equal to 2,240 pounds
• A metric ton is equal to 1,000 kilograms, or 2,204.62 pounds
THE METRIC SYSTEM
The metric system is an important part of international commerce and science and as a journalist you should understand it. The international decimal-based metric system is based on multiples of 10.
Meter: the basic unit for length based on a measure that equals one 10-millionth of the distance from the North Pole to the equator along the meridian running near Dunkirk in France and Barcelona in Spain.
Mass: one gram is the mass of one cubic centimeter of water at 0 degrees Celsius.
Newton: the metric unit of force; one Newton is a force that, applied to a one-kilogram object, will give the object an acceleration of one meter per second per second.
