Work, Mixture & Distance
Use rate × time = amount, and add rates when people work together.
The rules
- Distance = rate × time.
- Work: add rates. If A does a job in 6 hours and B in 3 hours, together their rate is 1/6 + 1/3.
- Mixtures: amount of pure substance = concentration × volume.
- Set up a table with rate, time, and amount.
Watch out: Averaging the times instead of adding the rates.
Worked example
Alex paints a fence in 6 hours, and Blake in 3 hours. How long do they take together?
- Rates: 1/6 + 1/3 = 1/2 job per hour.
- Time = 1 / (1/2) = 2 hours.
Answer: 2 hours
Try it yourself
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