Example

Solving a Work Application: Printing Presses

Apply the problem-solving strategy for work applications to find how long it takes two printing presses to complete a job together. If Press #1 takes 6 hours alone and Press #2 takes 12 hours alone, let tt be the hours needed together. In 1 hour, Press #1 completes 16\frac{1}{6} of the job, Press #2 completes 112\frac{1}{12} of the job, and together they complete 1t\frac{1}{t} of the job. The rational equation is 16+112=1t\frac{1}{6} + \frac{1}{12} = \frac{1}{t}. Multiply both sides by the least common denominator (LCD), 12t12t, to get 12t(16+112)=12t(1t)12t \left(\frac{1}{6} + \frac{1}{12}\right) = 12t \left(\frac{1}{t}\right). Distribute and simplify to obtain 2t+t=122t + t = 12, which becomes 3t=123t = 12, yielding t=4t = 4. When both presses are running together, it takes 4 hours to complete the job.

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Updated 2026-06-25

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Ch.7 Rational Expressions and Functions - Intermediate Algebra @ OpenStax

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