One of the formulas you will be given during the GED math test is:
distance = rate x time
which can be also written as
d = rt
Obviously using this formula will tell you the distance of a trip when you already have the speed (or rate) and the travel time.
For example, let’s say you traveled 55mph for 30 minutes. How far have you traveled. The first thing you need to do is to convert one of the units, since the speed is in distance per hour and the time you traveled is in minutes. Since your answer will likely be in miles, you should convert the minutes into hours in order to avoid doing another conversion from miles per minute back to miles per hour. How many hours is 30 minutes. Of course you already know thirty minutes is ½ an hour, but the mathematical way to arrive at that is to divide the number of minutes (30) by the total number of minutes in the unit (the 60 minutes in an hour):
Now you multiply ½ by 55 to arrive at the number of miles traveled, the distance.
55 x ½ (or .5) = 27.5
You traveled 27.5 miles.
You might be asked to calculate how much time it took to take a trip. In this situation you will likely be given the distance and the speed (rate) and the same formula:
d = rt
Now since what you want to know is the time (t) rather than the distance (d) you need to get t by itself on one side of the equation. Naturally you do this by dividing by the speed (r).
Time equals distance over rate. Time equals distance traveled divided by the speed of travel.
So let’s say you need to travel 15 miles by foot at 3 miles per hour. How long will it take you to travel 15 miles?
It will take you 5 hours.
You traveled 1,700 miles in two and a half days, how fast were you travelling?
Now you need to find r, rate or speed, so you need to change the formula again.
Rate (speed) equals distance divided by time.
Since you need to answer in miles per hour, you need to convert the 2 ½ into hours. Since there are 24 hours in a day, multiply 24 by 2 ½, which is 2.5.
There are 60 hours in 2 ½ days.
Now divide the distance by the time to get the speed.
You were traveling at about 28.3 mph.