Answer:
Since, an airplane descended 4,000 feet before landing.
Now, we have to determine the integer which represents the number of feet, the airplane was above the ground before its descent.
Before the descent, airplane was at the height of 4,000 feet.
And the distance above the ground is represented by the positive integers and distance below the ground is represented by the negative integers.
Since, 4,000 feet is the distance of airplane above the ground.
So, the airplane was +4,000 feet above the ground before its descent.
first to find average age add all the ages divide by number of ages 4
5+4=9
9+6=15
15+39=54
54/4=13.5
For standard deviation find the mean/average
13.5
then subtract the mean from each number/age
5-13.5=-8.5
4-13.5=-9.5
6-13.5=-7.5
39-13.5=25.5
then square each number
-8.5^2=-72.25
-9.5^2=-90.25
-7.5^2=-56.25
25.5^2=650.25
then find the mean/average of the new numbers
-72.25+-90.25+-56.25+650.25=431.5
431.5/4=107.85
then take the square root of the new mean/average

Answer:
33.75.
Step-by-step explanation:
The mean = sum of the numbers / the number count
= (34 + 31 + 32 + 38) / 4
= 135 / 4
= 33.75.
Answer: C
The -4 has an open circle and 0 has a closed circle