Answer:
8.94 seconds
Step-by-step explanation:
The ground is at height 0.
We set the equation equal to zero and solve for t.
h = -16 t^2 + 20*t + 1100
We want h = 0, so we get
-16 t^2 + 20*t + 1100 = 0
4t^2 - 5t - 275 = 0
[tex] t = \dfrac{-b \pm \sqrt{b^2 - 4ac}}{2a} [/tex]
[tex] t = \dfrac{-(-5) \pm \sqrt{(-5)^2 - 4(4)(-275)}}{2(4)} [/tex]
[tex] t = \dfrac{5 \pm \sqrt{25 + 4400}}{8} [/tex]
[tex] t = \dfrac{5 \pm \sqrt{4425}}{8} [/tex]
[tex] t = \dfrac{5 \pm 5\sqrt{177}}{8} [/tex]
[tex] t = 8.94 [\tex] or [/tex] t = -7.69 [/tex]
We discard the negative answer.
Answer: 8.94 seconds
