Printers P and Q working together print a job in hours. Printers Q and R together take hours, and P and R together take hours. How many hours would all three printers take working together?

Answer and explanation

Correct answer: C.

  1. Step 1: Express the hourly work rates for each pair: , , and .
  2. Step 2: Sum all three equations: .
  3. Step 3: Divide by to find the combined rate: job per hour. Taking the reciprocal gives the required time: .
Answer
.

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