Answer:
36.58% probability that one of the devices fail
Step-by-step explanation:
For each device, there are only two possible outcomes. Either it fails, or it does not fail. The probability of a device failling is independent of other devices. So we use the binomial probability distribution to solve this question.
Binomial probability distribution
The binomial probability is the probability of exactly x successes on n repeated trials, and X can only have two outcomes.

In which
is the number of different combinations of x objects from a set of n elements, given by the following formula.

And p is the probability of X happening.
A total of 15 devices will be used.
This means that 
Assume that each device has a probability of 0.05 of failure during the course of the monitoring period.
This means that 
What is the probability that one of the devices fail?
This is 


36.58% probability that one of the devices fail
Answer:
136
Step-by-step explanation:
15 plus 2 is 17,then multiplied by 8
Answer:
log₇t = ln t / ln 7
Step-by-step explanation:
Given:
log₇t
Computation:
We know that
logₐb = log b / log a
So,
log₇t = log t / log 7
= log₇t = ln t / ln 7