Answer:

Step-by-step explanation:
Set up the equation:
Since C(t) gives the number of cars purchased in the t-th year after 1998, then make the number of cars equal to 15 000 and solve for t - the year:
20t^2 = 15000
t^2 = 750
t = 
The year will be simply 1998 + 5 \sqrt{30}
Using a proportional relationship, we have that:
- a) The constant of proportionality is of 0.625, hence the equation is:
.
- b) The distance of two cities that are 5 miles apart is of 8 kilometers.
- c) When they are 200 kilometers apart, we have that the distance in miles is of
.
<h3>What is a proportional relationship?</h3>
- A <em>proportional relationship</em> is a function in which the <u>output variable is given by the input variable multiplied by a constant of proportionality</u>, that is:.

- In which k is the constant of proportionality.
Item a:
From the graph, when x = 8, y = 5, hence:




The constant of proportionality is of 0.625, hence the equation is:
.
Item b:
From the graph, when y = 5, x = 8, hence:
- The distance of two cities that are 5 miles apart is of 8 kilometers.
Item c:
When they are 200 kilometers apart, we have that the distance in miles is of
.
You can learn more about proportional relationship at brainly.com/question/13550871
Answer:
1.7 seconds
Step-by-step explanation:
we have

where
v is the initial velocity (in feet per second)
s represents the initial height (in feet)
In this problem we have
---> because the object is dropped

substitute

Remember that
When the chestnut hit the ground the value of H is equal to zero
so
For H=0

solve for t

therefore
The solution is t=1.7 sec