SOLUTION: A rock is propelled upward from the top of a building 80 feet tall at an initial velocity of 136 feet per second. The function that describes the height of the rock in terms of ti

Question 440187: A rock is propelled upward from the top of a building 80 feet tall at an initial velocity of 136 feet per second. The function that describes the height of the rock in terms of time t is f(t) = - 16t2 + 136t + 80. Determine the time at which the rock reaches its maximum height.
A. 8.5 sec
B. 4.25 sec
C. 3.4 sec
D. 6.8 sec

Answer by jorel1380(3719) (Show Source): You can put this solution on YOUR website!
16t2=136t
2t2=17t
t=17/2
The rock will return to its' starting point in 8.5 seconds, therefore, it will reach its apogee (highest point) in half that time, or 4.25 seconds.
16t2=68t
t2=4.25t
t=4.25..

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