MathChapter 14: Rational Expressions
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Card 1 of 20. Answer hidden.
Prompt
What represents one whole job?
Answer
\(1\).
Prompt
If a job takes \(t\) hours, what is the rate?
Answer
\(1/t\) job per hour.
Prompt
What is the core work formula?
Answer
Work done = rate × time.
Prompt
How are simultaneous independent work rates combined?
Answer
Add the rates.
Prompt
Should completion times be added?
Answer
No. Convert times to rates first.
Prompt
What does \(x/6\) mean in a work equation?
Answer
Work completed in \(x\) hours at \(1/6\) job per hour.
Prompt
What equation models two workers for \(x\) hours?
Answer
\(x/a+x/b=1\), where \(a,b\) are their solo times.
Prompt
How is combined time found from combined rate \(r\)?
Answer
Use \(1/r\) for one job.
Prompt
What sanity check applies to two positive rates?
Answer
Together-time must be less than the fastest solo time.
Prompt
How much work remains after \(w\) is completed?
Answer
\(1-w\).
Prompt
How should staged work be modeled?
Answer
Calculate work in each time interval, then add the contributions.
Prompt
What must happen before mixing minutes and hourly rates?
Answer
Convert all times to one unit.
Prompt
How many hours is 90 minutes?
Answer
\(3/2\) hours.
Prompt
What does a rate of \(2/5\) job per hour mean?
Answer
Two fifths of one job is completed each hour.
Prompt
If the target is three jobs, what replaces the right side 1?
Answer
\(3\).
Prompt
What answer distinction matters in a staged problem?
Answer
Total elapsed time versus time after another worker joins.
Prompt
Workers take 6 h and 4 h alone. What is their combined rate?
Answer
\(1/6+1/4=5/12\) job per hour.
Prompt
For rates \(1/6\) and \(1/4\), what is together-time?
Answer
\(1/(5/12)=12/5\) hours.
Prompt
Why can a negative time be rejected?
Answer
Time in the work context must be nonnegative; it cannot describe the requested duration.
Prompt
What five checks finish a work-rate solution?
Answer
Target work, stage contributions, units, positivity, and faster-together plausibility.
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