Answer:
Independent event
Step-by-step explanation:
Independent event is defined as events that will not influence each other. In this question, the combination lock has three separate wheels. Each wheel has one key out of 10 possible numbers. The key of the first wheel will not influence the number pool of second and third wheels. All of the wheels will have 10 possible numbers regardless. Therefore, the combined number is an independent event.
Answer:
We have to find the z critical value at 100% - 90% = 10% level of significance.
Since the normal distribution has two tails, we therefore, need to divide the significance level into two tails with each tail having area of 5%.
Now using the standard normal table, the z critical is:

Step One
Find the sum of the fractions for Monday and Tuesday
1/2 + 2/5
The common denominator for these 2 days is 10
1/2: 1*5/(2*5) = 5/10
2/5:2*2/(2*5) = 4/10
Add these two equivalent fractions together.
5/10 + 4/10 = 9/10
The first 2 days resulted in 9/10 of the shed being completed.
Step Two
Find out how much (in terms of fractions) is left of the shed.
Let the whole shed = 1
Let what has been done = 9/10
What remains is 1 - 9/10 = 1/10
Answer: 1/10 of the shed needs to be done