Work and Motion Problems: Rates That Add
Turn every worker and every traveler into a rate. Work rates add; speeds add when movers approach or separate, and subtract when one chases the other.
What it is
Work and motion problems are both about rates: how much gets done in one unit of time.
- In a work problem, a worker who finishes a job in 6 hours does 1/6 of the job every hour. Workers who work together add their rates.
- In a motion problem, a speed of 60 kph means 60 km every hour. Distance = speed × time. Two movers that approach each other or move apart add their speeds; a mover chasing another closes the gap at the difference of their speeds.
Why it matters on the exam
Work and motion items appear in every Numerical Ability set, and they have well-known traps: averaging or adding the times in a work problem, subtracting speeds when they should be added, and reading 2.5 hours as 2 hours 50 minutes. Once you think in rates, each item becomes one short equation.
At work, rates help you estimate how long a team needs for a task, or when a delivery will arrive.
- 4 hours
- 12.5 hours
- 15 hours
- 25 hours
The rest of this lesson, and every other lesson, is part of ReviewTayo.
Read moreIn the full lesson
- How to recognize it on the test
- What to look for (6 checks)
- All 4 rules and tools
- 4 worked examples, every step explained
- 6 common mistakes and how to fix them
- 3 exam techniques
- Remember: 5 key points
- Practice questions with explanations, and your progress saved
More Numerical Ability lessons
ReviewTayo has 47 lessons that follow the official scope of the exam, each with rules, worked examples, common mistakes and practice. Open one and read the first part.