We know that
speed=distance/time
solve for time
time=distance/speed
in this problem
<span>Marco runs at a rate of 6 miles per hour.
</span><span>Fernando funs at a rate of 7.2 miles per hour
Difference=7.2-6=1.2 miles/hour
so
speed=1.2 miles/hour
distance=0.3 miles
time=?
</span>time=distance/speed-----> 0.3/1.2-----> 0.25 hour-----> 0.25*60=15 minutes
<span>
the answer is
0.25 hour (15 minutes)
Alternative Method
Let
x---------> Fernando's distance when Marco is 0.3 miles apart
</span>Fernando funs at a rate of 7.2 miles per hour
<span>for distance =x
time=x/7.2------> equation 1
</span>Marco runs at a rate of 6 miles per hour.
for distance=x-0.30
time=(x-0.30)/6------> equation 2
equate equation 1 and equation 2
7.2*(x-0.3)=6x-----> 7.2x-2.16=6x
7.2x-6x=2.16------> x=2.16/1.2-------> x=1.8 miles
time=x/7.2-----1.8/7.2=0.25 hour
The 3rd answer, is correct.
Answer:
--- Standard deviation
Step-by-step explanation:
Given
See attachment for graph
Solving (a): Explain how the standard deviation is calculated.
<u>Start by calculating the mean</u>
To do this, we divide the sum of the products of grade and number of students by the total number of students;
i.e.

So, we have:



Next, calculate the variance using the following formula:

i.e subtract the mean from each dataset; take the squares; add up the squares; then divide the sum by the number of dataset
So, we have:



Lastly, take the square root of the variance to get the standard deviation


--- approximated
<em>Hence, the standard deviation is approximately 11.28</em>
Considering the calculated mean (i.e. 82.76), the standard deviation (i.e. 11.28) is small and this means that the grade of the students are close to the average grade.
Answer: x - 2.6 = 72.8
x is the number which Dan was thinking (x > 2.6)
we have:
x - 2.6 = 72.8
Step-by-step explanation: