City Guilds Model Questions Vol1 2025 Engineering Question 49

Practice objective / multiple choice question 49 from the 2025 City Guilds Model Questions Vol1 Engineering examination.

City Guilds Model Questions Vol1 2025 Engineering Objective / Multiple Choice Hard Difficulty
Question 49 CITY_GUILDS_MODEL_QUESTIONS_VOL1 • 2025 • ENGINEERING • objective

An equipment unit has a constant failure probability per hour of \(0.0002\) when operated without recent maintenance. Performing preventive maintenance reduces the failure probability to \(0.00005\) for the next 200 hours, after which the probability reverts to \(0.0002\) until the next maintenance. The cost of each preventive maintenance action is ₦500, while the cost incurred by a failure (including repair and downtime) is ₦5000. Assuming the unit operates continuously, determine the preventive‑maintenance interval (in hours) that minimises the expected cost per operating hour over the long run. State the optimal strategy.

Answer Options

A. Preventive maintenance every 200 hours; (minimum cost ≈ ₦1.5 per hour)
B. Preventive maintenance every 100 hours; (minimum cost ≈ ₦1.8 per hour)
C. Preventive maintenance every 50 hours; (minimum cost ≈ ₦2.5 per hour)
Correct Answer D. No preventive maintenance; interval → ∞ (minimum cost ≈ ₦1 per hour)
Correct Answer
D
Correct Option:
No preventive maintenance; interval → ∞ (minimum cost ≈ ₦1 per hour)

About This Question

This is City Guilds Model Questions Vol1 2025 Engineering Question 49. It is one of the objective questions from the 2025 City Guilds Model Questions Vol1 Engineering examination.

Difficulty level: Hard .

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