X = velocity of plane
y = velocity of wind
x - y = 1680/5 = 336 mph .....(1) [ plane flying against the wind]
&
x + y = 1680/4 = 420 mph....(2) [ plane flying with the wind]
Adding (1) and (2) to eliminate y gives
2x = 756
x = 378 mph is the speed of the plane with no wind.
Answer:
> a<-rnorm(20,50,6)
> a
[1] 51.72213 53.09989 59.89221 32.44023 47.59386 33.59892 47.26718 55.61510 47.95505 48.19296 54.46905
[12] 45.78072 57.30045 57.91624 50.83297 52.61790 62.07713 53.75661 49.34651 53.01501
Then we can find the mean and the standard deviation with the following formulas:
> mean(a)
[1] 50.72451
> sqrt(var(a))
[1] 7.470221
Step-by-step explanation:
For this case first we need to create the sample of size 20 for the following distribution:

And we can use the following code: rnorm(20,50,6) and we got this output:
> a<-rnorm(20,50,6)
> a
[1] 51.72213 53.09989 59.89221 32.44023 47.59386 33.59892 47.26718 55.61510 47.95505 48.19296 54.46905
[12] 45.78072 57.30045 57.91624 50.83297 52.61790 62.07713 53.75661 49.34651 53.01501
Then we can find the mean and the standard deviation with the following formulas:
> mean(a)
[1] 50.72451
> sqrt(var(a))
[1] 7.470221
Using the combination formula, it is found that Julia can take 15 combinations.
<h3>What is the combination formula?</h3>
is the number of different combinations of x objects from a set of n elements, given by:

For this problem, 4 students are taken from a set of 6, hence the number of combinations is given as follows:

More can be learned about the combination formula at brainly.com/question/25821700
#SPJ1
Answer:A.4
Step-by-step explanation: