Tami thought that the perimiter is length plus width, which gave her 100. The actual width is 20
Answer: Option D

Step-by-step explanation:
Note that the projectile height as a function of time is given by the quadratic equation

To find the maximum height of the projectile we must find the maximum value of the quadratic function.
By definition the maximum value of a quadratic equation of the form
is located on the vertex of the parabola:

Where 
In this case the equation is: 
Then

So:


If each garden takes 20 minutes to clean, it will take him (20 x 4) to clean the gardens.
20 x 4 = 100
80 minutes
or 1 hour and 10 minutes.