Question

**WILL MEDAL**

A ball is thrown upward from the top of a building. The function below shows the height of the ball in relation to sea level, ft, in feet, at different times t in seconds:

f(t) = -16t^2 + 34t + 80

The average rate of change of f(t) from t = 5 seconds to t = 7 seconds is _____ feet per second.

Answer 1

I just need my answer checked...

I got -308

Answer 2

Only the sign is correct.
Did you use
average rate of change = \(\dfrac{\Delta f(t)}{\Delta t}\)
where \(\Delta t\) = 7-5=2 seconds?

Answer 3

I did -466 - 150/7 - 5

Answer 4

which got me -616/2, then I got -308

Answer 5

ok, remember that when you deal with a fraction, all numerators and denominators have implied brackets, so you understand the concept, but have a little slip in calculating. It actually is
\(\dfrac{\color{red}{(}-466-(-150)\color{red}{)}}{2}=(-466-(-150))/2=(-466+150)/2=?\)

Answer 6

OH! Okay, so it's actually -158 ft/per sec

Answer 7

Exactly! Well done!