Answer:
Step-by-step explanation:
Let the initial number be x
<u>Sold 1/3x, and now has:</u>
<u>Bought 84 more and now got 178:</u>
- 2/3x + 84 = 178
- 2/3x = 94
- x = 94 ÷ 2/3
- x = 94 × 3/2
- x = 141
Jessica had 141 records initially
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
Have a wonderful day today
All Ages:- 9, 13, 9, 10, 10, 9, 10, 10, 11, 9
No. of ages = 10
Mean = 
Mean of all Ages = 10 years
<h3>Hope This Helps</h3>