ISRO | ISRO CS 2020 | Question 4

What is the availability of the software with following reliability figures.

Mean Time Between Failures (MTBF) is 20 days
Mean Time To Repair (MTTR) is 20 hours 

(A) 90%
(B) 96%
(C) 24%
(D) 50%

Answer: (B)
Explanation: Convert into the same unit then apply the formula.
Software availability,

= MTBF / (MTBF + MTTR)
= 20*24 / (20*24 + 20)
= 480 / 500
= 0.96
= 96 %

Option (D) is correct.
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