In our example, the steps are:
-
Distance is the same for both women.
- Choose x = Barbara's rate (in mph). Bonnie's rate (in mph) = x + 15
- Barbara's distance: d = rt = x(2) = 2x
- Bonnie's distance: d = rt = (x + 15)(1.5) = 1.5x + 22.5
-
2x = 1.5x + 22.5
-
x = 45
Barbara travels at 45 miles per hour. Bonnie travels at 60 miles per hour.
Here is another example:
Jeff and Jed are twins who run at exactly the same speed. 45 minutes after they begin running, Jeff pulls a muscle and has to stop. Jed finishes the run -- 4 more miles. If Jed runs for 75 minutes total, how many miles did Jeff run before he stopped?
- Rate is the same for both men.
- Choose x = Jeff's distance. Jed's distance = x + 4
- Jeff's rate: r =
=
- Jed's rate: r =
=
-
=
-
x = 6
Jeff ran 6 miles.