<span>Answer:
21 document= 1 error
120 document= 1 hour
in three and a half hours= 21 mistakes</span>
The answer is letter is C. 19.5 Because you divide
Answer:

Step-by-step explanation:
To solve this problem we need to be familiar with the formula for the surface area of a cone:

We are given the length of a side and the diameter, to calculate the radius divide the diameter in half:

To calculate the height of the cone, we must use the Pythagorean Theorem:

We can treat the side length as the hypotenuse
, the radius as the base
, and solve for height
. Set the expression up like this:

Now we can plug into our original formula:

So if in 2 hours you drove 80 miles the in 1 hour you have to have driven 40 miles (80m/2h)
so you have to divide the 1200 miles by the 40mph to find out how many hours the trip will take (1200m/40mph=30h)