CMA Foundation · Fundamentals of Business Mathematics and Statistics · Ratios, Variations and Proportions
A contractor in Jaipur estimates that 18 workers can complete a road-repair job in 30 days. Because of a deadline, the job must be completed in 20 days. Assuming all workers are equally efficient, how many workers are needed?
The contractor needs 27 workers. Number of workers varies inversely with the days available, so total work stays at 18 × 30 = 540 worker-days. Dividing 540 by the 20 days allowed gives 27 workers to finish the job on time.
- A12
- B20
- C27Correct
- D36
Explanation
Workers vary inversely with days, so workers × days is constant: 18 × 30 = 540 worker-days. Workers needed = 540/20 = 27. Check: 27 × 20 = 540. Choosing 12 comes from wrongly treating the relation as direct (18 × 20/30).
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