Algebra: Chapter 8, Lesson 5, page 380.
Motion Problems
D-R-T Problems (otherwise known as DIRT problems). `D` is the distance, `R` is the rate (or speed like miles per hour [mph] or kilometers per hour [kph] or feet per second [ft/sec]) and `T` is the time. Be careful and make sure that if the rate is in mph, then the time has to be in hours. If the rate is in feet/sec, then the time has to match and be in seconds as well.
For those type of problems that have 2 people starting off, remember that the first person’s time is `t`, but the second person (who leaves later) actually has `t – x` time where x is the time delay of the second person leaving. For example if one person leaves at `t` and the second leaves 2 hours later, then the second person’s time is `t – 2`.
REMEMBER, diagrams are great to get you to understand what you are looking for. The tables in the book are also good techniques. The more pictures or diagrams you have, the better chance you have of understanding what steps you have to go through! GO SLOW!!
Here are some links to excellent D-R-T examples at the PurpleMath website. Its easier to link to these than show you the same thing!
Two of tonight’s homework problems solved by MrE are here! Just click it!
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Algebra 1a: Chapter 3, Quiz #6
No homework tonight, we begin Chapter 4 tomorrow!