ITPEC IP April 2020 Question 15
ITPEC IP April 2020 — Question 15 of 100
Adding the third series device decreases system availability by 10% relative to the two-device system. Two devices in series have availability 0.9² = 0.81. Three have 0.9³ = 0.729. The decrease is 0.081, and 0.081 divided by the reference 0.81 equals 0.10.
Answer (c)
Why not others:
- a series system requires every device to work, so availability cannot increase or remain unchanged
- the relative decrease is 10%, not 30%
Key rule: Multiply independent component availabilities in series, then measure percentage change relative to the stated reference.
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