A keyboarder's speed over a 6-min interval is given by the following function, where W(t) is the speed, in words per minute, at time t. W(t) = - 5t + 20t + 60 a) Find the speed at the beginning of the interval. b) Find the maximum speed and when it occurs. c) Find the average speed over the 6-min interval.

You purchased a car for $30 000. It depreciates by 25% of its current value every year. a) Write a function that can be used to model the value of the car after x years. b) How much will the car be worth 3 years after it is purchased? c) How long would it take for the car to depreciate to a value of $20 000?

If a bullet from a pistol is fired straight up from the ground, its height t seconds after it is fired will be s (t) = -16t2 + 1280t feet (neglecting air resistance).  a. Find the velocity function b. How long will it take the bullet to fall back to the ground? c. With what velocity will the bullet hit the ground?

The height of the falling sheet of paper, in feet from the ground, is given by s(t)=-1.5t+9 after t seconds. ​ When will the sheet of paper reach the ground? ​ a. after 3 seconds b. after 15 seconds c. after 9 seconds d. after 7.5 seconds e. after 6 seconds