Correct answer is: P(x<6) is 0.123 and it is usual.
Solution:-
Given that the time a person takes to decide which shoes to purchase follows normal distribution. Which has mean = 8.21 minutes and standard deviation 1.90
Then probability of individual takes less than 6 minutes is
P(X<6) = 
= 
= 0.1230
Typically we say an event with a probability less than 5% is unusual.
But here P(X<6) = 0.123 is greater than 5% hence this is usual.

Both the numerator and denominator are continuous at

, which means the quotient rule for limits applies:

Perhaps you meant to write that

instead? In that case, you would have
Answer:
56.7
Step-by-step explanation:
We know
mean = sum / count, with count being the amount of papers corrected in this case. We want to find the sum of all the papers as well as the count to figure out the mean of all papers.
For Tony's papers,
mean = sum / count
50 = sum / 40
multiply both sides by 40 to isolate the sum
sum = 50 * 40 = 2000
For Alice's papers,
mean = sum / count
70 = sum / 20
multiply both sides by 20 to isolate the sum
70 * 20 = sum = 1400
The total sum of all 60 papers is equal to the sum of 40 papers + the sum of the remaining 20 papers, or 2000 + 1400 = 3400. The mean of the 60 papers is therefore
mean = sum / count
mean = 3400/60 ≈ 56.7
It is 12 since 1/6=6^-1=6
implies 2*6=12