# Math Tools for Journalists Part 3

By Megan Wanner

Many journalists do not realize it, but time, rate and distance problems are just as relevant now as they were during middle school math class.  These numbers can give stories a whole new dimension of accuracy that readers appreciate when trying to fully grasp a situation such as a car accident where the driver of one car thought he had time to cross in front of another car.

It is important not to only rely on the numbers given to you as a reporter, but to calculate your own in order to provide greater accuracy for your audience.  This may take more time, but it’s more important to be accurate than timely.

The basic formula for time, rate and distance is the same; the equation is just reworked to obtain each number.  One of the most important things to remember with these problems is to keep the units of measurement the same and convert when necessary.

Formula

Distance = rate x time

Rate = distance / time

Time = distance / rate

Speed, velocity, acceleration and momentum are also important measurements to know how to calculate.  Speed measures how fast something is going.  Velocity measures how fast something is going and in what direction it is traveling.  Typically, reporters only need to calculate speed.

While a speedometer will give you “instantaneous speed,” reporters find more usage in average speed, calculated by dividing the traveled distance by the time it took to travel the distance.  As average speed is another word for rate, it can be plugged into the rate equation.

Average speed = distance / time

Acceleration is the starting velocity subtracted from the ending velocity then divided by time.

Acceleration = (ending velocity – starting velocity) / time

The acceleration due to the force of gravity is 9.8 meters per second per second.  This acceleration is the same for all falling objects barring the force of friction.  When working with falling objects, you typically only know the distance it fell.  Determining the speed at which an object was traveling when it hit the ground requires a simple manipulation of the acceleration equation.

All moving objects have momentum, the force needed to stop an object from moving.

Momentum = mass x velocity

As a journalist, there are two good ways to explain measurements to your reader.  The first is by analogy, the second with simple numbers.

Analogies are a good way to give your readers a visual of how big something is.  For example, if a large tree takes down a power line, it is much easier to describe to readers how large the tree is by comparing it to a building its size.

Simple numbers are used when exact accuracy is needed in a story.  For this it is important to be familiar with area, perimeter, square feet, square yards, circumference and radius to write stories about construction, real estate, etc.

Perimeter is simply the measurement around an object determined by adding the lengths of all the sides together.

Area is the measurement of the region inside an object.

Area of square and rectangle = length x width

Area of triangle = ½base x height

The radius of a circle is the distance from the middle of the circle to any edge of the circle.  You need to know the radius in order to calculate the circumference or distance around the circle.

Volume details can add important context and accuracy to articles.  The basic formula for volume is length multiplied by width multiplied by height.

Although the metric system is disliked in America, it is actually useful and used for an assortment of measurements.  As it is based on multiples of 10, it is actually easier to use and convert than the English standard version we are used to as it is only a matter of multiplying or dividing by multiples of 10.

Basic Definitions:

Meter—basic unit for length

Gram—basic unit for mass

Newton—basic unit for force

Liter—basic unit for volume

Celcius—basic unit for temperature

Prefixes:

micro (1 millionth) 0.000001

milli (1 thousandth) 0.001

centi (1 hundredth) 0.01

deci (1 tenth) 0.1

no prefix 1.0

deka 10

hector 100

kilo 1,000

mega 1,000,000

giga 1,000,000,000

tera 1,000,000,000,000

Practice Problems:

A car is traveling at a constant speed of 70 miles per hour to its destination 200 miles away.  How long will it take the car to get there?

Time = distance / rate

Time = 200 / 70

Time = 2 hours and 51 minutes

The local park is building a rectangular swimming pool for its community.  The pool is 30 feet by 20 feet.  In order to stake out the area for the pool, the committee must know how much area the pool is going to take up.

Area = length x width

Area = 30 x 20

Area = 600 feet2

In order to build a sidewalk around the pool, the committee must know what the perimeter of the pool will be.

Perimeter = 2lengh + 2width

Perimeter = 2(30) + 2(20)

Perimeter = 100 feet

A box of bananas is 3 feet long, 2 feet wide and a foot deep.  What is the volume of the box?

Volume = length x width x height

Volume = 3 x 2 x 1

Volume = 6 feet3

A sidewalk is measured to be 40 meters long.  How many centimeters is this?

40 meters x 100 = 4,000 centimeters